Interview › Databases & Caching
How would you use Redis for distributed locking, and what are the caveats?
Databases & Caching · Advanced level
Answer
Redis distributed locks commonly use SET key value NX PX ttl with a unique token and compare-and-delete release. They are useful for efficiency locks but require caution for correctness-critical workflows.
Technical explanation
Rate limits can use INCR/EXPIRE or sorted sets, ideally through Lua for atomicity.
Distributed locks should use SET key value NX PX ttl with unique token and safe compare-and-delete release; they are better for efficiency than hard correctness.
Security baseline is private subnets, SG restrictions, TLS, AUTH/ACLs, secret rotation, and no public exposure.
Hands-on example
Rate limit example:
MULTI
INCR rl:tenant:42:minute:202606301015
EXPIRE rl:tenant:42:minute:202606301015 120
EXEC
Lock example:
SET lock:refresh:product:123 <uuid> NX PX 5000
Release only if GET lock value matches your uuid. Never DEL blindly.
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