Distributed Locking in Practice: Guarantees, Failure Scenarios and Better Alternatives (4/4)

The most reliable distributed systems often minimize coordination as much as possible while still preserving correctness. Instead of introducing additional coordination mechanisms, experienced engineers often redesign systems to avoid coordination altogether. This approach is supported by several key principles and techniques.

One approach is to rely on a database's built-in data integrity mechanisms to enforce business rules. For example, instead of using a distributed lock to prevent duplicate email registrations, a unique constraint can be applied directly to the database schema. This ensures data integrity without the need for external coordination. The flow becomes simpler: insert the customer record directly, and the database handles any conflicts or duplicates.

Another technique is optimistic concurrency control, which eliminates the need for distributed locks when multiple instances attempt to modify the same record. Instead of blocking access, multiple instances can proceed concurrently. When a conflict is detected (e.g., version mismatch), the operation can be retried with up-to-date state. This approach provides high throughput, minimizes coordination overhead, and simplifies recovery models.

Idempotency is another key concept that eliminates many locking problems. By including an idempotency key with each request, the system can check if the operation has already been processed. If so, the previous result is returned, preventing unnecessary work. This approach ensures that repeating the same operation does not cause unintended side effects, removing the need for coordination altogether.