sharding - MongoDB shard key chosen strategy in IM system

Question

I'm developing an IM system, I use MongoDB shard to store the history messages. The query demand is only based on the sessions of two users.

The shard key is:

sh.shardCollection("message.message", {"sessionId": "hashed", "msgId": 1})

sessionId field is uin1-uin2 (concatenation of two user's uin), msgId field is monotonically increasing. The objective is both user's messages should be located only on one shard, so we can load the session's history messages efficiently.

Is it a good shard key to acheive the objective? thank you.

Answer 1

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