I have just installed Percona 3.4 and see that the Memory Engine is a really nice option. Is is possible to use WiredTiger for one database and Memory Engine for another? I can’t work out how if so!!
Unfortunately, the MongoDB storage API is designed so only one engine may be active at a time. One thing maybe people do is have different shards for different workloads, as each replica-set could have a different engine they use. This is something we are looking at the possibility of changing but I do not know a timeline or probability of that feature just yet.
Thanks David. I think I will have a few shards based on the workload.