Backend & systems·Data modelling and storage engines
one point lookup turns into six file reads because the key could be in any of the levels the compactor has not merged yet.
Read amplification
How many physical reads it takes to answer one logical read. LSM engines trade write amplification down and read amplification up, mitigating it with bloom filters and compaction. It shows up as a p99 that is far worse than the median, because the tail is the requests that had to check every level.