Database / RocksDB Basics Interview Questions
What is a Bloom Filter in RocksDB?
A Bloom filter is a compact, probabilistic data structure attached to each SSTable that can quickly tell whether a key is definitely not present, without needing to actually read the file.
- Can produce false positives, occasionally saying a key might be present when it isn't, but never false negatives
- Lets RocksDB skip reading SSTables entirely when the filter confirms a key definitely isn't there
- Dramatically reduces unnecessary disk reads, especially important when a key lookup would otherwise have to check many SSTables
Bloom filters are one of the main reasons RocksDB's read performance stays reasonable despite data being spread across many separate, immutable files.
Can a Bloom filter produce a false positive?
What does a Bloom filter let RocksDB skip?
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