Janusgraph does some internal activities due to which there are spikes in starting 1-2 runs.. (even at 10 QPS) and after that it gets stable. Once it's stable, no spikes are observed, is it expected behaviour, that needed some warm-up run to make it stable? Using Back-end Cassandra CQL.
Cassandra can exhibit behavior like this on startup. If there are files in the commitlog (directory), those will validate and write their data to disk. If there are a lot of them, there can be a bit of an increase in resource consumption.