Mongo Manual said
we can use embedded documents and arrays to capture relationships between data in a single document structure instead of normalizing across multiple documents and collections, this single-document atomicity obviates the need for multi-document transactions for many practical use cases.
So we tend to use embed documents，but sometimes one document can be very large，in our project it may reach 30M or more, so we must split it and keep reference relation, it gonna be very complicated and this way mongo doesn’t support muti-doc txn in single server, it’s so wired.
Redis has supported RedisJson Module and the limit is 512M, I wish mongo increase this limit and support JsonPath.
And i want to know why mongo only support muti-doc txn in replica and shard, sometimes we want to test transaction but mush deploy replica, it’s troublesome