As high throughput clusters grow and documents become larger, the MongoDB balancer may begin impacting workloads.

I'd like the ability to throttle the speed at which the balancer or chunk migrator runs such that impact is minimised.

Is there any plan to implement distributed transaction that involves more than one data stores (for e.g. an RDBMS and Mongo)? We have one such requirement and tried a simple POC by creating a simple class extending XAResource (MongoXAResource implements XAResource) and overriding below methods.

@Override

public void commit(Xid xid, boolean b) throws XAException {

    clientSession.commitTransaction();

}

@Override

public void rollback(Xid xid) throws XAException {

    clientSession.abortTransaction();

}

It appears to work but i think there is a lot more to do. Is there any plan to implement by MongoDB team?

Add support for repairing a single collection instead of what is currently available to repair an entire database via db.repairDatabase()

Per the Server Support Matrix https://docs.mongodb.com/manual/installation/ support for Ubuntu 20 is in MongoDB Server version 4.4+ but not 4.2.
We would like to see the currently supported MongoDB Server version 4.2 available on the Ubuntu 20.4 LTS distribution.

Suppose I have collection of documents { entityId, entity }, where entity is names of other collections I would like to make aggregation with lookup and be able to pass entity value to $lookup from and as

db.collection.aggregation([{ $lookup: { from: '$entity', let: { entityId: '$entityId' }, pipeline: [{ $match: { $expr: { $eq: ['$_id', '$$entityId'] } } }], as: '$entity' } }])

As of mongo v4.4.4 that seems not working.

If a new version of MongoDB will include a new version of MozJS (ex https://jira.mongodb.org/browse/SERVER-29286) and this version will break any existing scripts it would be ideal if this was documented.

For example, with MongoDB 4.2 "value".contains() no longer worked in scripts and had to be converted to "value".includes()

CHoose an oplog event to set the resume token for, instead of needing to run the change stream for system to create a resume token

Why: Concerns about many stream re-reading a full oplog if failure before finding first event

In the options for Mongo DB Log Settings, there is only
Max Percent of Disk
Total Number of files

A new option for
Number of Days to keep

Would be useful

An expression index is one where the value being indexed is the result of an expression, like lower casing a string.

http://en.wikipedia.org/wiki/Expression_index
http://www.postgresql.org/docs/8.1/static/indexes-expressional.html

we've already seen a full text search and it will be awesome if you manage to implement partial version :)

a couple of customer a shifting from MongoDB to other DBs like Redis or even PostreSQL as count is too slow on MongoDB when there are a lot of document to count even with use of indexes

To improve network security, please create an option to Deny specific Network Adresses to MongoDB Cluster.

Create an option for the user to replicate data from one MongoDB Cluster to another MongoDB Cluster inside the account. We don't need to migrate data, I need replicate data from an Production Cluster to an Dev/Test Cluster. Thanks.

Change streams currently return only the new version of the documents.

If there were an option that could be set on the collection for the change streams to also return the old version of the document, it would simplify any business logic that requires the old version.

As a DBA or Data Architect, I want to be able to enforce data governance policies like schema control. Users of MongoDB cannot change the schema however DBA or named individuals have the ability to change the schema.

SQL based option to create view using multiple collections or databases

We are in the process of implementing AWS SSO across our Organisation and wanted to tie this in with mongodb-aws for database authentication.
Unfortunately we have been informed the 2 services are not compatible.

This would be a really useful add on to improve management of our systems.

Would be a great great feature if we can create a VPC between ATLAS/MongoDB/AWS and Heroku/AWS.
Thanks.
Adailton Silva