# KV Pair Storage in RocksDB (1/2)
+ Lock cf

+ key -> start_ts/PUT

+ key+commit_ts -> start_ts/PUT
+ Write cf

+ key_start_ts  -> value
+ Default cf
+ Use two-phase commit protocol (2PC) for distributed transactions.
+ In the preparation phase,  write default and lock cfs (the write operations are atomic).
+ In the commit phase, delete lock cfs and write write cf (the delete and write operations are atomic).

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