diff --git a/federationsender/storage/cosmosdb/inbound_peeks_table.go b/federationsender/storage/cosmosdb/inbound_peeks_table.go
index da9c8d095..6775cc1f5 100644
--- a/federationsender/storage/cosmosdb/inbound_peeks_table.go
+++ b/federationsender/storage/cosmosdb/inbound_peeks_table.go
@@ -149,7 +149,7 @@ func (s *inboundPeeksStatements) InsertInboundPeek(
 	// stmt := sqlutil.TxStmt(txn, s.insertInboundPeekStmt)
 
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getInboundPeek(s, ctx, s.getPartitionKey(roomID), cosmosDocId)
@@ -193,7 +193,7 @@ func (s *inboundPeeksStatements) RenewInboundPeek(
 
 	// _, err = sqlutil.TxStmt(txn, s.renewInboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	// _, err = sqlutil.TxStmt(txn, s.renewInboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
@@ -222,7 +222,7 @@ func (s *inboundPeeksStatements) SelectInboundPeek(
 
 	// "SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_inbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getPartitionKey(roomID), docId)
 
 	// row := sqlutil.TxStmt(txn, s.selectInboundPeeksStmt).QueryRowContext(ctx, roomID)
diff --git a/federationsender/storage/cosmosdb/outbound_peeks_table.go b/federationsender/storage/cosmosdb/outbound_peeks_table.go
index cf9ec1830..8b39a6c5c 100644
--- a/federationsender/storage/cosmosdb/outbound_peeks_table.go
+++ b/federationsender/storage/cosmosdb/outbound_peeks_table.go
@@ -145,7 +145,7 @@ func (s *outboundPeeksStatements) InsertOutboundPeek(
 	// stmt := sqlutil.TxStmt(txn, s.insertOutboundPeekStmt)
 	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getOutboundPeek(s, ctx, s.getPartitionKey(roomID), cosmosDocId)
@@ -190,7 +190,7 @@ func (s *outboundPeeksStatements) RenewOutboundPeek(
 
 	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	// _, err = sqlutil.TxStmt(txn, s.renewOutboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
@@ -219,7 +219,7 @@ func (s *outboundPeeksStatements) SelectOutboundPeek(
 	// "SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_outbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
 
 	// 	UNIQUE (room_id, server_name, peek_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, serverName, peekID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, serverName, peekID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	// row := sqlutil.TxStmt(txn, s.selectOutboundPeeksStmt).QueryRowContext(ctx, roomID)
diff --git a/federationsender/storage/cosmosdb/queue_edus_table.go b/federationsender/storage/cosmosdb/queue_edus_table.go
index f08ee65bb..039fe8cee 100644
--- a/federationsender/storage/cosmosdb/queue_edus_table.go
+++ b/federationsender/storage/cosmosdb/queue_edus_table.go
@@ -145,7 +145,7 @@ func (s *queueEDUsStatements) InsertQueueEDU(
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS federationsender_queue_edus_json_nid_idx
 	//     ON federationsender_queue_edus (json_nid, server_name);
-	docId := fmt.Sprintf("%d_%s", nid, eduType)
+	docId := fmt.Sprintf("%d,%s", nid, eduType)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := queueEDUCosmos{
diff --git a/federationsender/storage/cosmosdb/queue_pdus_table.go b/federationsender/storage/cosmosdb/queue_pdus_table.go
index 99e679c6e..7edcc1e99 100644
--- a/federationsender/storage/cosmosdb/queue_pdus_table.go
+++ b/federationsender/storage/cosmosdb/queue_pdus_table.go
@@ -157,7 +157,7 @@ func (s *queuePDUsStatements) InsertQueuePDU(
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS federationsender_queue_pdus_pdus_json_nid_idx
 	//     ON federationsender_queue_pdus (json_nid, server_name);
-	docId := fmt.Sprintf("%d_%s", nid, serverName)
+	docId := fmt.Sprintf("%d,%s", nid, serverName)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := queuePDUCosmos{
diff --git a/internal/cosmosdbutil/partition_offset_table.go b/internal/cosmosdbutil/partition_offset_table.go
index cb206ae60..9d8e46b25 100644
--- a/internal/cosmosdbutil/partition_offset_table.go
+++ b/internal/cosmosdbutil/partition_offset_table.go
@@ -86,7 +86,7 @@ type PartitionOffsetStatements struct {
 
 func (s PartitionOffsetStatements) getCollectionName() string {
 	// Include the Prefix
-	tableName := fmt.Sprintf("%s_%s", s.prefix, s.tableName)
+	tableName := fmt.Sprintf("%s,%s", s.prefix, s.tableName)
 	return cosmosdbapi.GetCollectionName(s.db.DatabaseName, tableName)
 }
 
@@ -193,7 +193,7 @@ func (s *PartitionOffsetStatements) upsertPartitionOffset(
 		// stmt := TxStmt(txn, s.upsertPartitionOffsetStmt)
 
 		//     UNIQUE (topic, partition)
-		docId := fmt.Sprintf("%s_%d", topic, partition)
+		docId := fmt.Sprintf("%s,%d", topic, partition)
 		cosmosDocId := cosmosdbapi.GetDocumentId(s.db.CosmosConfig.TenantName, s.getCollectionName(), docId)
 
 		dbData, _ := getPartitionOffset(s, ctx, s.getPartitionKey(topic), cosmosDocId)
diff --git a/internal/naffka/naffkacosmosdb/naffka_topics_table.go b/internal/naffka/naffkacosmosdb/naffka_topics_table.go
index 2e123e6ea..924ba2be7 100644
--- a/internal/naffka/naffkacosmosdb/naffka_topics_table.go
+++ b/internal/naffka/naffkacosmosdb/naffka_topics_table.go
@@ -299,7 +299,7 @@ func (t *topicsStatements) InsertTopics(
 	// stmt := sqlutil.TxStmt(txn, t.insertTopicsStmt)
 
 	// 	UNIQUE (topic_nid, message_offset)
-	docId := fmt.Sprintf("%d_%d", topicNID, messageOffset)
+	docId := fmt.Sprintf("%d,%d", topicNID, messageOffset)
 	cosmosDocId := cosmosdbapi.GetDocumentId(t.DB.cosmosConfig.ContainerName, t.getCollectionNameMessages(), docId)
 
 	data := messageCosmos{
diff --git a/keyserver/storage/cosmosdb/cross_signing_keys_table.go b/keyserver/storage/cosmosdb/cross_signing_keys_table.go
index f654bde64..99a5f6603 100644
--- a/keyserver/storage/cosmosdb/cross_signing_keys_table.go
+++ b/keyserver/storage/cosmosdb/cross_signing_keys_table.go
@@ -149,7 +149,7 @@ func (s *crossSigningKeysStatements) UpsertCrossSigningKeysForUser(
 		return fmt.Errorf("unknown key purpose %q", keyType)
 	}
 	// 	PRIMARY KEY (user_id, key_type)
-	docId := fmt.Sprintf("%s_%s", userID, keyType)
+	docId := fmt.Sprintf("%s,%s", userID, keyType)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getCrossSigningKeys(s, ctx, s.getPartitionKey(userID), cosmosDocId)
diff --git a/keyserver/storage/cosmosdb/cross_signing_sigs_table.go b/keyserver/storage/cosmosdb/cross_signing_sigs_table.go
index 30037d830..4763424a7 100644
--- a/keyserver/storage/cosmosdb/cross_signing_sigs_table.go
+++ b/keyserver/storage/cosmosdb/cross_signing_sigs_table.go
@@ -183,7 +183,7 @@ func (s *crossSigningSigsStatements) UpsertCrossSigningSigsForTarget(
 	// 	" VALUES($1, $2, $3, $4, $5)"
 
 	// 	PRIMARY KEY (origin_user_id, target_user_id, target_key_id)
-	docId := fmt.Sprintf("%s_%s_%s", originUserID, targetUserID, targetKeyID)
+	docId := fmt.Sprintf("%s,%s,%s", originUserID, targetUserID, targetKeyID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getCrossSigningSigs(s, ctx, s.getPartitionKey(targetUserID), cosmosDocId)
diff --git a/keyserver/storage/cosmosdb/device_keys_table.go b/keyserver/storage/cosmosdb/device_keys_table.go
index d18023262..67bd6424d 100644
--- a/keyserver/storage/cosmosdb/device_keys_table.go
+++ b/keyserver/storage/cosmosdb/device_keys_table.go
@@ -325,7 +325,7 @@ func (s *deviceKeysStatements) SelectDeviceKeysJSON(ctx context.Context, keys []
 		// err := s.selectDeviceKeysStmt.QueryRowContext(ctx, key.UserID, key.DeviceID).Scan(&keyJSONStr, &streamID, &displayName)
 
 		//     UNIQUE (user_id, device_id)
-		docId := fmt.Sprintf("%s_%s", key.UserID, key.DeviceID)
+		docId := fmt.Sprintf("%s,%s", key.UserID, key.DeviceID)
 		cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 		response, err := getDeviceKey(s, ctx, s.getPartitionKey(key.UserID), cosmosDocId)
@@ -437,7 +437,7 @@ func (s *deviceKeysStatements) InsertDeviceKeys(ctx context.Context, txn *sql.Tx
 
 	for _, key := range keys {
 		//     UNIQUE (user_id, device_id)
-		docId := fmt.Sprintf("%s_%s", key.UserID, key.DeviceID)
+		docId := fmt.Sprintf("%s,%s", key.UserID, key.DeviceID)
 		cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 		dbData := &deviceKeyCosmosData{
diff --git a/keyserver/storage/cosmosdb/key_changes_table.go b/keyserver/storage/cosmosdb/key_changes_table.go
index 72e81174b..86ced845c 100644
--- a/keyserver/storage/cosmosdb/key_changes_table.go
+++ b/keyserver/storage/cosmosdb/key_changes_table.go
@@ -120,7 +120,7 @@ func (s *keyChangesStatements) InsertKeyChange(ctx context.Context, partition in
 	// " DO UPDATE SET user_id = $3"
 
 	// 	UNIQUE (partition, offset)
-	docId := fmt.Sprintf("%d_%d", partition, offset)
+	docId := fmt.Sprintf("%d,%d", partition, offset)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getKeyChangeUser(s, ctx, s.getPartitionKey(), cosmosDocId)
diff --git a/keyserver/storage/cosmosdb/one_time_keys_table.go b/keyserver/storage/cosmosdb/one_time_keys_table.go
index a3972e070..15e6e681a 100644
--- a/keyserver/storage/cosmosdb/one_time_keys_table.go
+++ b/keyserver/storage/cosmosdb/one_time_keys_table.go
@@ -275,7 +275,7 @@ func (s *oneTimeKeysStatements) InsertOneTimeKeys(
 		algo, keyID := keys.Split(keyIDWithAlgo)
 
 		//     UNIQUE (user_id, device_id, key_id, algorithm)
-		docId := fmt.Sprintf("%s_%s_%s_%s", keys.UserID, keys.DeviceID, keyID, algo)
+		docId := fmt.Sprintf("%s,%s,%s,%s", keys.UserID, keys.DeviceID, keyID, algo)
 		cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 		data := oneTimeKeyCosmos{
diff --git a/mediaapi/storage/cosmosdb/media_repository_table.go b/mediaapi/storage/cosmosdb/media_repository_table.go
index 63622269b..b7e30edb1 100644
--- a/mediaapi/storage/cosmosdb/media_repository_table.go
+++ b/mediaapi/storage/cosmosdb/media_repository_table.go
@@ -139,7 +139,7 @@ func (s *mediaStatements) insertMedia(
 	// VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS mediaapi_media_repository_index ON mediaapi_media_repository (media_id, media_origin);
-	docId := fmt.Sprintf("%s_%s", mediaMetadata.MediaID, mediaMetadata.Origin)
+	docId := fmt.Sprintf("%s,%s", mediaMetadata.MediaID, mediaMetadata.Origin)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := mediaRepositoryCosmos{
@@ -194,7 +194,7 @@ func (s *mediaStatements) selectMedia(
 	// SELECT content_type, file_size_bytes, creation_ts, upload_name, base64hash, user_id FROM mediaapi_media_repository WHERE media_id = $1 AND media_origin = $2
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS mediaapi_media_repository_index ON mediaapi_media_repository (media_id, media_origin);
-	docId := fmt.Sprintf("%s_%s", mediaMetadata.MediaID, mediaMetadata.Origin)
+	docId := fmt.Sprintf("%s,%s", mediaMetadata.MediaID, mediaMetadata.Origin)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	// err := s.selectMediaStmt.QueryRowContext(
diff --git a/mediaapi/storage/cosmosdb/thumbnail_table.go b/mediaapi/storage/cosmosdb/thumbnail_table.go
index a2cea0f6b..426680b9e 100644
--- a/mediaapi/storage/cosmosdb/thumbnail_table.go
+++ b/mediaapi/storage/cosmosdb/thumbnail_table.go
@@ -131,7 +131,7 @@ func (s *thumbnailStatements) insertThumbnail(
 	// stmt := sqlutil.TxStmt(txn, s.insertThumbnailStmt)
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS mediaapi_thumbnail_index ON mediaapi_thumbnail (media_id, media_origin, width, height, resize_method);
-	docId := fmt.Sprintf("%s_%s_%d_%d_%s",
+	docId := fmt.Sprintf("%s,%s,%d,%d,%s",
 		thumbnailMetadata.MediaMetadata.MediaID,
 		thumbnailMetadata.MediaMetadata.Origin,
 		thumbnailMetadata.ThumbnailSize.Width,
@@ -200,7 +200,7 @@ func (s *thumbnailStatements) selectThumbnail(
 	// SELECT content_type, file_size_bytes, creation_ts FROM mediaapi_thumbnail WHERE media_id = $1 AND media_origin = $2 AND width = $3 AND height = $4 AND resize_method = $5
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS mediaapi_thumbnail_index ON mediaapi_thumbnail (media_id, media_origin, width, height, resize_method);
-	docId := fmt.Sprintf("%s_%s_%d_%d_%s",
+	docId := fmt.Sprintf("%s,%s,%d,%d,%s",
 		mediaID,
 		mediaOrigin,
 		width,
diff --git a/roomserver/storage/cosmosdb/membership_table.go b/roomserver/storage/cosmosdb/membership_table.go
index a2c415f61..2c1f677fe 100644
--- a/roomserver/storage/cosmosdb/membership_table.go
+++ b/roomserver/storage/cosmosdb/membership_table.go
@@ -268,7 +268,7 @@ func (s *membershipStatements) InsertMembership(
 	// " ON CONFLICT DO NOTHING"
 
 	// 		UNIQUE (room_nid, target_nid)
-	docId := fmt.Sprintf("%d_%d", roomNID, targetUserNID)
+	docId := fmt.Sprintf("%d,%d", roomNID, targetUserNID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	// " ON CONFLICT DO NOTHING"
@@ -317,7 +317,7 @@ func (s *membershipStatements) SelectMembershipForUpdate(
 	// "SELECT membership_nid FROM roomserver_membership" +
 	// " WHERE room_nid = $1 AND target_nid = $2"
 
-	docId := fmt.Sprintf("%d_%d", roomNID, targetUserNID)
+	docId := fmt.Sprintf("%d,%d", roomNID, targetUserNID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	response, err := getMembership(s, ctx, s.getPartitionKey(), cosmosDocId)
@@ -335,7 +335,7 @@ func (s *membershipStatements) SelectMembershipFromRoomAndTarget(
 	// 	"SELECT membership_nid, event_nid, forgotten FROM roomserver_membership" +
 	// 	" WHERE room_nid = $1 AND target_nid = $2"
 
-	docId := fmt.Sprintf("%d_%d", roomNID, targetUserNID)
+	docId := fmt.Sprintf("%d,%d", roomNID, targetUserNID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	response, err := getMembership(s, ctx, s.getPartitionKey(), cosmosDocId)
 	if response != nil {
@@ -432,7 +432,7 @@ func (s *membershipStatements) UpdateMembership(
 	// "UPDATE roomserver_membership SET sender_nid = $1, membership_nid = $2, event_nid = $3, forgotten = $4" +
 	// " WHERE room_nid = $5 AND target_nid = $6"
 
-	docId := fmt.Sprintf("%d_%d", roomNID, targetUserNID)
+	docId := fmt.Sprintf("%d,%d", roomNID, targetUserNID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	dbData, err := getMembership(s, ctx, s.getPartitionKey(), cosmosDocId)
 
@@ -693,7 +693,7 @@ func (s *membershipStatements) UpdateForgetMembership(
 	// "UPDATE roomserver_membership SET forgotten = $1" +
 	// " WHERE room_nid = $2 AND target_nid = $3"
 
-	docId := fmt.Sprintf("%d_%d", roomNID, targetUserNID)
+	docId := fmt.Sprintf("%d,%d", roomNID, targetUserNID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	dbData, err := getMembership(s, ctx, s.getPartitionKey(), cosmosDocId)
 
diff --git a/roomserver/storage/cosmosdb/state_block_table.go b/roomserver/storage/cosmosdb/state_block_table.go
index 5b898db93..997ef1835 100644
--- a/roomserver/storage/cosmosdb/state_block_table.go
+++ b/roomserver/storage/cosmosdb/state_block_table.go
@@ -18,7 +18,7 @@ package cosmosdb
 import (
 	"context"
 	"database/sql"
-	"encoding/hex"
+	"encoding/base64"
 	"fmt"
 	"sort"
 
@@ -144,7 +144,7 @@ func (s *stateBlockStatements) BulkInsertStateData(
 	// ).Scan(&id)
 
 	// 	state_block_hash BLOB UNIQUE,
-	docId := hex.EncodeToString(nids.Hash())
+	docId := base64.StdEncoding.EncodeToString(nids.Hash())
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	//See if it exists
diff --git a/roomserver/storage/cosmosdb/transactions_table.go b/roomserver/storage/cosmosdb/transactions_table.go
index c245ffa20..ba86c0578 100644
--- a/roomserver/storage/cosmosdb/transactions_table.go
+++ b/roomserver/storage/cosmosdb/transactions_table.go
@@ -68,9 +68,8 @@ func (s *transactionStatements) getCollectionName() string {
 	return cosmosdbapi.GetCollectionName(s.db.databaseName, s.tableName)
 }
 
-func (s *transactionStatements) getPartitionKey(transactionID string) string {
-	uniqueId := transactionID
-	return cosmosdbapi.GetPartitionKeyByUniqueId(s.db.cosmosConfig.TenantName, s.getCollectionName(), uniqueId)
+func (s *transactionStatements) getPartitionKey() string {
+	return cosmosdbapi.GetPartitionKeyByCollection(s.db.cosmosConfig.TenantName, s.getCollectionName())
 }
 
 func getTransaction(s *transactionStatements, ctx context.Context, pk string, docId string) (*transactionCosmosData, error) {
@@ -114,7 +113,7 @@ func (s *transactionStatements) InsertTransaction(
 	// VALUES ($1, $2, $3, $4)
 
 	// 		PRIMARY KEY (transaction_id, session_id, user_id)
-	docId := fmt.Sprintf("%s_%d_%s", transactionID, sessionID, userID)
+	docId := fmt.Sprintf("%s,%d,%s", transactionID, sessionID, userID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := transactionCosmos{
@@ -125,7 +124,7 @@ func (s *transactionStatements) InsertTransaction(
 	}
 
 	var dbData = transactionCosmosData{
-		CosmosDocument: cosmosdbapi.GenerateDocument(s.getCollectionName(), s.db.cosmosConfig.TenantName, s.getPartitionKey(transactionID), cosmosDocId),
+		CosmosDocument: cosmosdbapi.GenerateDocument(s.getCollectionName(), s.db.cosmosConfig.TenantName, s.getPartitionKey(), cosmosDocId),
 		Transaction:    data,
 	}
 
@@ -151,10 +150,10 @@ func (s *transactionStatements) SelectTransactionEventID(
 	// WHERE transaction_id = $1 AND session_id = $2 AND user_id = $3
 
 	// 		PRIMARY KEY (transaction_id, session_id, user_id)
-	docId := fmt.Sprintf("%s_%d_%s", transactionID, sessionID, userID)
+	docId := fmt.Sprintf("%s,%d,%s", transactionID, sessionID, userID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
-	response, err := getTransaction(s, ctx, s.getPartitionKey(transactionID), cosmosDocId)
+	response, err := getTransaction(s, ctx, s.getPartitionKey(), cosmosDocId)
 
 	if err != nil {
 		return "", err
diff --git a/signingkeyserver/storage/cosmosdb/server_key_table.go b/signingkeyserver/storage/cosmosdb/server_key_table.go
index 6a10a8c3b..d037d9175 100644
--- a/signingkeyserver/storage/cosmosdb/server_key_table.go
+++ b/signingkeyserver/storage/cosmosdb/server_key_table.go
@@ -204,7 +204,7 @@ func (s *serverKeyStatements) upsertServerKeys(
 	// stmt := sqlutil.TxStmt(txn, s.upsertServerKeysStmt)
 
 	// 	UNIQUE (server_name, server_key_id)
-	docId := fmt.Sprintf("%s_%s", string(request.ServerName), string(request.KeyID))
+	docId := fmt.Sprintf("%s,%s", string(request.ServerName), string(request.KeyID))
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getServerKey(s, ctx, s.getPartitionKey(), cosmosDocId)
diff --git a/syncapi/storage/cosmosdb/account_data_table.go b/syncapi/storage/cosmosdb/account_data_table.go
index bad466016..3637a4ce0 100644
--- a/syncapi/storage/cosmosdb/account_data_table.go
+++ b/syncapi/storage/cosmosdb/account_data_table.go
@@ -137,7 +137,7 @@ func (s *accountDataStatements) InsertAccountData(
 	}
 
 	//     UNIQUE (user_id, room_id, type)
-	docId := fmt.Sprintf("%s_%s_%s", userID, roomID, dataType)
+	docId := fmt.Sprintf("%s,%s,%s", userID, roomID, dataType)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getAccountDataType(s, ctx, s.getPartitionKey(), cosmosDocId)
diff --git a/syncapi/storage/cosmosdb/backwards_extremities_table.go b/syncapi/storage/cosmosdb/backwards_extremities_table.go
index d19c20427..a518391d9 100644
--- a/syncapi/storage/cosmosdb/backwards_extremities_table.go
+++ b/syncapi/storage/cosmosdb/backwards_extremities_table.go
@@ -141,7 +141,7 @@ func (s *backwardExtremitiesStatements) InsertsBackwardExtremity(
 	// _, err = sqlutil.TxStmt(txn, s.insertBackwardExtremityStmt).ExecContext(ctx, roomID, eventID, prevEventID)
 
 	// 	PRIMARY KEY(room_id, event_id, prev_event_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, eventID, prevEventID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, eventID, prevEventID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getBackwardExtremity(s, ctx, s.getPartitionKey(roomID), cosmosDocId)
diff --git a/syncapi/storage/cosmosdb/current_room_state_table.go b/syncapi/storage/cosmosdb/current_room_state_table.go
index db14c8edb..2b5d8c04e 100644
--- a/syncapi/storage/cosmosdb/current_room_state_table.go
+++ b/syncapi/storage/cosmosdb/current_room_state_table.go
@@ -391,7 +391,7 @@ func (s *currentRoomStateStatements) UpsertRoomState(
 	// )
 
 	// " ON CONFLICT (room_id, type, state_key)" +
-	docId := fmt.Sprintf("%s_%s_%s", event.RoomID(), event.Type(), *event.StateKey())
+	docId := fmt.Sprintf("%s,%s,%s", event.RoomID(), event.Type(), *event.StateKey())
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	membershipData := ""
@@ -556,7 +556,7 @@ func (s *currentRoomStateStatements) SelectStateEvent(
 	var res []byte
 
 	// " ON CONFLICT (room_id, type, state_key)" +
-	docId := fmt.Sprintf("%s_%s_%s", roomID, evType, stateKey)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, evType, stateKey)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var response, err = getEvent(s, ctx, s.getPartitionKey(), cosmosDocId)
 
diff --git a/syncapi/storage/cosmosdb/filter_table.go b/syncapi/storage/cosmosdb/filter_table.go
index c6bb154dc..6b94b275e 100644
--- a/syncapi/storage/cosmosdb/filter_table.go
+++ b/syncapi/storage/cosmosdb/filter_table.go
@@ -117,7 +117,7 @@ func (s *filterStatements) SelectFilter(
 	// err := s.selectFilterStmt.QueryRowContext(ctx, localpart, filterID).Scan(&filterData)
 
 	// 	UNIQUE (id, localpart)
-	docId := fmt.Sprintf("%s_%s", localpart, filterID)
+	docId := fmt.Sprintf("%s,%s", localpart, filterID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var response, err = getFilter(s, ctx, s.getPartitionKey(), cosmosDocId)
 
@@ -208,7 +208,7 @@ func (s *filterStatements) InsertFilter(
 	}
 
 	// 	UNIQUE (id, localpart)
-	docId := fmt.Sprintf("%s_%d", localpart, seqID)
+	docId := fmt.Sprintf("%s,%d", localpart, seqID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	var dbData = filterCosmosData{
diff --git a/syncapi/storage/cosmosdb/memberships_table.go b/syncapi/storage/cosmosdb/memberships_table.go
index 7c3560757..913f4a62e 100644
--- a/syncapi/storage/cosmosdb/memberships_table.go
+++ b/syncapi/storage/cosmosdb/memberships_table.go
@@ -146,7 +146,7 @@ func (s *membershipsStatements) UpsertMembership(
 	// )
 
 	// 	UNIQUE (room_id, user_id, membership)
-	docId := fmt.Sprintf("%s_%s_%s", event.RoomID(), *event.StateKey(), membership)
+	docId := fmt.Sprintf("%s,%s,%s", event.RoomID(), *event.StateKey(), membership)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getMembership(s, ctx, s.getPartitionKey(), cosmosDocId)
diff --git a/syncapi/storage/cosmosdb/output_room_events_topology_table.go b/syncapi/storage/cosmosdb/output_room_events_topology_table.go
index 6e9f45d6f..e50d01da9 100644
--- a/syncapi/storage/cosmosdb/output_room_events_topology_table.go
+++ b/syncapi/storage/cosmosdb/output_room_events_topology_table.go
@@ -192,7 +192,7 @@ func (s *outputRoomEventsTopologyStatements) InsertEventInTopology(
 	// 	" ON CONFLICT DO NOTHING"
 
 	// 	UNIQUE(topological_position, room_id, stream_position)
-	docId := fmt.Sprintf("%d_%s_%d", event.Depth(), event.RoomID(), pos)
+	docId := fmt.Sprintf("%d,%s,%d", event.Depth(), event.RoomID(), pos)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	var err error
diff --git a/syncapi/storage/cosmosdb/peeks_table.go b/syncapi/storage/cosmosdb/peeks_table.go
index e904f0426..6795e08d3 100644
--- a/syncapi/storage/cosmosdb/peeks_table.go
+++ b/syncapi/storage/cosmosdb/peeks_table.go
@@ -168,7 +168,7 @@ func (s *peekStatements) InsertPeek(
 	// " VALUES ($1, $2, $3, $4, $5, false)"
 
 	//     UNIQUE(room_id, user_id, device_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomID, userID, deviceID)
+	docId := fmt.Sprintf("%s,%s,%s", roomID, userID, deviceID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	dbData, _ := getPeek(s, ctx, s.getPartitionKey(), cosmosDocId)
diff --git a/syncapi/storage/cosmosdb/receipt_table.go b/syncapi/storage/cosmosdb/receipt_table.go
index b16970461..90affd3c1 100644
--- a/syncapi/storage/cosmosdb/receipt_table.go
+++ b/syncapi/storage/cosmosdb/receipt_table.go
@@ -120,7 +120,7 @@ func (r *receiptStatements) UpsertReceipt(ctx context.Context, txn *sql.Tx, room
 	// " DO UPDATE SET id = $7, event_id = $8, receipt_ts = $9"
 
 	// 	CONSTRAINT syncapi_receipts_unique UNIQUE (room_id, receipt_type, user_id)
-	docId := fmt.Sprintf("%s_%s_%s", roomId, receiptType, userId)
+	docId := fmt.Sprintf("%s,%s,%s", roomId, receiptType, userId)
 	cosmosDocId := cosmosdbapi.GetDocumentId(r.db.cosmosConfig.ContainerName, r.getCollectionName(), docId)
 
 	data := receiptCosmos{
diff --git a/userapi/storage/accounts/cosmosdb/account_data_table.go b/userapi/storage/accounts/cosmosdb/account_data_table.go
index 898dbc777..d18732c2e 100644
--- a/userapi/storage/accounts/cosmosdb/account_data_table.go
+++ b/userapi/storage/accounts/cosmosdb/account_data_table.go
@@ -100,9 +100,9 @@ func (s *accountDataStatements) insertAccountData(
 	// 	ON CONFLICT (localpart, room_id, type) DO UPDATE SET content = $4
 	id := ""
 	if roomID == "" {
-		id = fmt.Sprintf("%s_%s", localpart, dataType)
+		id = fmt.Sprintf("%s,%s", localpart, dataType)
 	} else {
-		id = fmt.Sprintf("%s_%s_%s", localpart, roomID, dataType)
+		id = fmt.Sprintf("%s,%s,%s", localpart, roomID, dataType)
 	}
 
 	docId := id
diff --git a/userapi/storage/accounts/cosmosdb/key_backup_table.go b/userapi/storage/accounts/cosmosdb/key_backup_table.go
index adc9b0456..00f4746ef 100644
--- a/userapi/storage/accounts/cosmosdb/key_backup_table.go
+++ b/userapi/storage/accounts/cosmosdb/key_backup_table.go
@@ -188,7 +188,7 @@ func (s *keyBackupStatements) insertBackupKey(
 	// 	ctx, userID, key.RoomID, key.SessionID, version, key.FirstMessageIndex, key.ForwardedCount, key.IsVerified, string(key.SessionData),
 	// )
 	// CREATE UNIQUE INDEX IF NOT EXISTS e2e_room_keys_idx ON account_e2e_room_keys(user_id, room_id, session_id, version);
-	docId := fmt.Sprintf("%s_%s_%s_%s", userID, key.RoomID, key.SessionID, version)
+	docId := fmt.Sprintf("%s,%s,%s,%s", userID, key.RoomID, key.SessionID, version)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := keyBackupCosmos{
@@ -228,7 +228,7 @@ func (s *keyBackupStatements) updateBackupKey(
 	// )
 
 	// CREATE UNIQUE INDEX IF NOT EXISTS e2e_room_keys_idx ON account_e2e_room_keys(user_id, room_id, session_id, version);
-	docId := fmt.Sprintf("%s_%s_%s_%s", userID, key.RoomID, key.SessionID, version)
+	docId := fmt.Sprintf("%s,%s,%s,%s", userID, key.RoomID, key.SessionID, version)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	item, err := getKeyBackup(s, ctx, s.getPartitionKey(userID), cosmosDocId)
diff --git a/userapi/storage/accounts/cosmosdb/key_backup_version_table.go b/userapi/storage/accounts/cosmosdb/key_backup_version_table.go
index 20d66cd33..9ed269c8c 100644
--- a/userapi/storage/accounts/cosmosdb/key_backup_version_table.go
+++ b/userapi/storage/accounts/cosmosdb/key_backup_version_table.go
@@ -144,7 +144,7 @@ func (s *keyBackupVersionStatements) insertKeyBackup(
 	}
 	// err = txn.Stmt(s.insertKeyBackupStmt).QueryRowContext(ctx, userID, algorithm, string(authData), etag).Scan(&versionInt)
 	// CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_e2e_room_keys_versions(user_id, version);
-	docId := fmt.Sprintf("%s_%d", userID, versionInt)
+	docId := fmt.Sprintf("%s,%d", userID, versionInt)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := keyBackupVersionCosmos{
@@ -181,7 +181,7 @@ func (s *keyBackupVersionStatements) updateKeyBackupAuthData(
 		return fmt.Errorf("invalid version")
 	}
 	// CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_e2e_room_keys_versions(user_id, version);
-	docId := fmt.Sprintf("%s_%d", userID, versionInt)
+	docId := fmt.Sprintf("%s,%d", userID, versionInt)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	item, err := getKeyBackupVersion(s, ctx, s.getPartitionKey(userID), cosmosDocId)
@@ -212,7 +212,7 @@ func (s *keyBackupVersionStatements) updateKeyBackupETag(
 		return fmt.Errorf("invalid version")
 	}
 	// CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_e2e_room_keys_versions(user_id, version);
-	docId := fmt.Sprintf("%s_%d", userID, versionInt)
+	docId := fmt.Sprintf("%s,%d", userID, versionInt)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	item, err := getKeyBackupVersion(s, ctx, s.getPartitionKey(userID), cosmosDocId)
@@ -243,7 +243,7 @@ func (s *keyBackupVersionStatements) deleteKeyBackup(
 		return false, fmt.Errorf("invalid version")
 	}
 	// CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_e2e_room_keys_versions(user_id, version);
-	docId := fmt.Sprintf("%s_%d", userID, versionInt)
+	docId := fmt.Sprintf("%s,%d", userID, versionInt)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	item, err := getKeyBackupVersion(s, ctx, s.getPartitionKey(userID), cosmosDocId)
@@ -313,7 +313,7 @@ func (s *keyBackupVersionStatements) selectKeyBackup(
 		return
 	}
 	// CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_e2e_room_keys_versions(user_id, version);
-	docId := fmt.Sprintf("%s_%d", userID, versionInt)
+	docId := fmt.Sprintf("%s,%d", userID, versionInt)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	res, err := getKeyBackupVersion(s, ctx, s.getPartitionKey(userID), cosmosDocId)
diff --git a/userapi/storage/accounts/cosmosdb/threepid_table.go b/userapi/storage/accounts/cosmosdb/threepid_table.go
index 2eb18c3b6..6fa06c50f 100644
--- a/userapi/storage/accounts/cosmosdb/threepid_table.go
+++ b/userapi/storage/accounts/cosmosdb/threepid_table.go
@@ -146,7 +146,7 @@ func (s *threepidStatements) insertThreePID(
 		ThreePID:  threepid,
 	}
 
-	docId := fmt.Sprintf("%s_%s", threepid, medium)
+	docId := fmt.Sprintf("%s,%s", threepid, medium)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var dbData = threePIDCosmosData{
 		CosmosDocument: cosmosdbapi.GenerateDocument(s.getCollectionName(), s.db.cosmosConfig.TenantName, s.getPartitionKey(), cosmosDocId),
@@ -171,7 +171,7 @@ func (s *threepidStatements) deleteThreePID(
 	ctx context.Context, threepid string, medium string) (err error) {
 
 	// "DELETE FROM account_threepid WHERE threepid = $1 AND medium = $2"
-	docId := fmt.Sprintf("%s_%s", threepid, medium)
+	docId := fmt.Sprintf("%s,%s", threepid, medium)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var options = cosmosdbapi.GetDeleteDocumentOptions(s.getPartitionKey())
 	_, err = cosmosdbapi.GetClient(s.db.connection).DeleteDocument(
diff --git a/userapi/storage/devices/cosmosdb/devices_table.go b/userapi/storage/devices/cosmosdb/devices_table.go
index aed388b75..15f8f3b35 100644
--- a/userapi/storage/devices/cosmosdb/devices_table.go
+++ b/userapi/storage/devices/cosmosdb/devices_table.go
@@ -188,7 +188,7 @@ func (s *devicesStatements) insertDevice(
 	//     access_token TEXT PRIMARY KEY,
 	// 		UNIQUE (localpart, device_id)
 	// HACK: check for duplicate PK as we are using the UNIQUE key for the DocId
-	docId := fmt.Sprintf("%s_%s", localpart, id)
+	docId := fmt.Sprintf("%s,%s", localpart, id)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 
 	data := deviceCosmos{
@@ -227,7 +227,7 @@ func (s *devicesStatements) deleteDevice(
 	ctx context.Context, id, localpart string,
 ) error {
 	// "DELETE FROM device_devices WHERE device_id = $1 AND localpart = $2"
-	docId := fmt.Sprintf("%s_%s", localpart, id)
+	docId := fmt.Sprintf("%s,%s", localpart, id)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var options = cosmosdbapi.GetDeleteDocumentOptions(s.getPartitionKey())
 	var _, err = cosmosdbapi.GetClient(s.db.connection).DeleteDocument(
@@ -301,7 +301,7 @@ func (s *devicesStatements) updateDeviceName(
 	ctx context.Context, localpart, deviceID string, displayName *string,
 ) error {
 	// "UPDATE device_devices SET display_name = $1 WHERE localpart = $2 AND device_id = $3"
-	docId := fmt.Sprintf("%s_%s", localpart, deviceID)
+	docId := fmt.Sprintf("%s,%s", localpart, deviceID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var item, exGet = getDevice(s, ctx, s.getPartitionKey(), cosmosDocId)
 	if exGet != nil {
@@ -354,7 +354,7 @@ func (s *devicesStatements) selectDeviceByID(
 	ctx context.Context, localpart, deviceID string,
 ) (*api.Device, error) {
 	// "SELECT display_name FROM device_devices WHERE localpart = $1 and device_id = $2"
-	docId := fmt.Sprintf("%s_%s", localpart, deviceID)
+	docId := fmt.Sprintf("%s,%s", localpart, deviceID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var response, exGet = getDevice(s, ctx, s.getPartitionKey(), cosmosDocId)
 	if exGet != nil {
@@ -422,7 +422,7 @@ func (s *devicesStatements) updateDeviceLastSeen(ctx context.Context, localpart,
 	lastSeenTs := time.Now().UnixNano() / 1000000
 
 	// "UPDATE device_devices SET last_seen_ts = $1, ip = $2 WHERE localpart = $3 AND device_id = $4"
-	docId := fmt.Sprintf("%s_%s", localpart, deviceID)
+	docId := fmt.Sprintf("%s,%s", localpart, deviceID)
 	cosmosDocId := cosmosdbapi.GetDocumentId(s.db.cosmosConfig.TenantName, s.getCollectionName(), docId)
 	var item, exGet = getDevice(s, ctx, s.getPartitionKey(), cosmosDocId)
 	if exGet != nil {