Implement a distributed lock with Redis SET NX EX and safe Lua-based release

Documented steps

1. Acquire the lock atomically: `SET resource_name my_random_token NX EX 30000` - succeeds (returns OK) only if the key didn't exist, sets a 30s auto-expiry. Redis returns nil if locked by someone else.
2. Use a long, non-guessable random token (e.g. 16+ random bytes hex) as the value so you can identify who holds the lock.
3. Retry acquire on failure with a short backoff if a second of contention is acceptable.
4. Release the lock safely with a Lua script that deletes the key ONLY if the value still matches your token - prevents deleting a lock that expired and was re-acquired by another client: `if redis.call("get",KEYS[1]) == ARGV[1] then return redis.call("del",KEYS[1]) else return 0 end` via `EVAL ... 1 resource_name my_random_token`.
5. Never use a plain `DEL` for release - if your lock expired and another client took it, DEL deletes their lock and breaks mutual exclusion.
6. For stronger guarantees across multiple Redis masters, consider the canonical Redlock algorithm (acquire from N/2+1 of N masters) - the Redis docs explicitly recommend Redlock over the single-instance SET NX pattern where fault tolerance matters.
7. In redis-py, use a client-side Lua script via `r.eval(script, 1, key, token)` for atomic delete.