Exactly. You really should avoid doing performance optimizations without measurements that show improvement as well as provide some coverage against performance

Exactly. You really should avoid doing performance optimizations without measurements that show improvement as well as provide some coverage against performance regressions. Here's an example, Thrift (as used in Hector, a Cassandra client), had someone make a performance improvement: https://issues.apache.org/jira/browse/THRIFT-959 https://issues.apache.org/jira/browse/THRIFT-959 The discussion has a lot of "shoulds", and one measurement of latency distributions, but no measurement of typical workloads or bulk inserts. Turns out, that caused at least a 30% performance regression: https://issues.apache.org/jira/browse/THRIFT-1121 https://issues.apache.org/jira/browse/THRIFT-1121