Thanks for the data! I think I may have different use cases than are covered by your benchmarks.
Do you often do that many independent $incs (or any query) in a single second? I have gotten much better performance by using `BulkWrite` to do a bunch of small updates in a batch.
To go to a specific example from the "Driver Benchmark" on the link from your first reply:
client[:users].insert_one(name: Digest::MD5.hexdigest(index.to_s))
I notice in this specific example that there's no separation of the hashing from the query timing. so I might try to do the hashing first then time just the inserts. I would also a batch of `insertOne`s and then do a bulk write so I'm making much fewer queries. I will often pick some random size like 1,000 queries or so and do the `bulkWrite ` when I have accumulated that many queries, have surpassed some time (like if it has been more than 0.5s since the last update) or if there's no more items to process. Additionally if the order of the inserts doesn't matter using `ordered: false` can provide additional speedup.
For me the limiting factor is mostly around the performance of BulkWrite. I haven't hit any performance bottlenecks there that would merit benchmarking different ways to use it, but I would mostly be trying to fine tune things like how to group the items in a BulkWrite for optimal performance if I did.
Even in the case of one-off queries it almost always feels faster on 7+ than earlier versions. As I mentioned the one bottleneck we hit with migration was that we had some queries where we were querying on fields that were not properly indexed and in those cases performance tanked horribly to the point where some queries actually stopped working. However, once we added an index the queries were always faster than on the old version. When we did hit problems, it took only a few minutes to figure out what to index then everything was fine. We didn't have to make changes to our application or the queries themselves to fix any issues we had.