Comment by junto

At a guess CosmosDb NoSql was a good choice for dumping user contexts sharded rather than use Postgres schema or JSONB. Citus is the obvious choice for this with Postgres but Azure had poor support until recently 2024 they have preview Azure Database for Postgres with Elastic Clusters, which is basically Azure Database for Postgres Flexible Server with Citus extension installed. In the end they aren’t paying Microsoft what usual customer are, so even though CosmosDb NoSql is expensive (RU based) and the SDK is horrible, it probably served as a good stopgap until elastic clusters is fully out of preview. That’s my guess anyway.