REF: https://www.mongodb.com/docs/manual/release-notes/7.0-upgrade/
The second is the replica set.
Don’t worry, upgrading is just a simple task, just do a good job of backup and compatibility testing, and check the release for the contents of version changes.
Before you upgrade MongoDB, check that you’re using a MongoDB 7.0-compatible driver. Consult the driver documentation for your specific driver to verify compatibility with MongoDB 7.0.
Upgraded deployments that run on incompatible drivers might encounter unexpected or undefined behavior.
What is this mongodb7.0 driver? How to understand what is my current driver?
Compatibility Changes in MongoDB 7.0
storageDetails - do not use
FreeMonitoring - do not understand what is it, but look like do not use
Queryable Encryption General Availability - have no idea what is it
Backward-Incompatible Features
Collections with encryptedFields with [range indexes] - Have no idea what is it, but look like I don’t use it
Compound wildcard indexes require FCV 7.0 or greater. A pre-7.0 mongod does not start if you are using one or more compound wildcard indexes. - What is it?
Config servers that have collections with changeStreamPreAndPostImages enabled - have no idea what is it, but I think I don’t use it
Time series collections with custom bucketing parameters - I hope I don’t use it
Have no idea what is it:
Intra-Node Authentication
Starting in MongoDB 7.0, you can configure servers to authenticate X.509 certificates as cluster members identified by attributes or extension values. You can also override this configuration to accept alternate certificates during a rolling upgrade.
What is it not clear too:
Cluster Configuration
Active setClusterParameter parameter operations prevent feature Compatibility Version (FCV) from successful completion.