How do you implement Distributed Locks with Redis across multiple Node.js servers?

Short answer

Use SET with NX and PX options to store a random token with a timeout, and release the lock with a Lua script that verifies the token.

Explanation

When several Node.js server instances run a critical operation (such as debiting a balance or reserving a single seat), in-memory variables are not enough. Acquire the lock atomically through Redis: SET lock_key my_unique_token NX PX 30000. Release it only through a Lua Script so you do not delete a lock that expired and was acquired by another server.

Code example

// Lua script To release the atomic lock
const releaseScript = `
  if redis.call("get", KEYS[1]) == ARGV[1] then
    return redis.call("del", KEYS[1])
  else
    return 0
  end
`;

Common mistakes

• Releasing the lock with a simple DEL command without checking whether the token still belongs to the current operation.

Follow-up questions

• What is the N+1 problem in database queries, and how does DataLoader solve it in Node.js?

Sources

• Redis docs — Distributed Locks with Redis