From the design:
"Test a varying workload that first applies cache pressure (many write transactions with one outstanding incomplete read transaction), then floods a server with PIT requests, then applies cache pressure again."
SERVER-31767 is introducing a snapshot history window within which a mongod guarantees service of reads, along with a few new server parameter knobs to handle cache pressure. Cache pressure can build as we keep too many snapshots open and the cache and server become immobilized, so we must test out configurations.
PIT requests are currently using the stable_timestamp, so this ticket may depend on further progress of the global PIT reads project, which depends on