When using RocksDBStateBackend and enabling state.backend.rocksdb.memory.managed and state.backend.rocksdb.memory.fixed-per-slot, flink will strictly limited rocksdb memory usage which contains "write buffer" and "block cache". With these options rocksdb stores index and filters in block cache, because in default options index/filters can grows unlimited.
But it's lead another issue, if high-priority cache(configure by state.backend.rocksdb.memory.high-prio-pool-ratio) can't fit all index/filters blocks, it will load all metadata from disk when cache missed, and program went extremely slow. According to Partitioned Index Filters, we can enable two-level index having acceptable performance when index/filters cache missed.
Enable these options can get over 10x faster in my case, I think we can add an option state.backend.rocksdb.partitioned-index-filters and default value is false, so we can use this feature easily.
 Partitioned Index Filters: https://github.com/facebook/rocksdb/wiki/Partitioned-Index-Filters
 Deduplicate scenario, state.backend.rocksdb.memory.fixed-per-slot=256M, SSD, elapsed time 4.91ms -> 0.33ms.