The correct choice is Optimistic concurrency control.

Optimistic concurrency control is appropriate for a managed SQL instance that must serve many simultaneous users because it avoids long lived locks and blocking. Each transaction proceeds using a working snapshot and the system checks for conflicts at commit time and retries only the transactions that actually conflict, which improves throughput for high concurrency workloads.

Exclusive locks are not ideal because they force serialization of access to records and create contention that reduces scalability and increases latency in environments with many concurrent writers.

Snapshot isolation alone does not eliminate write conflicts in the same way as optimistic control and it can allow anomalies such as write skew. It is an isolation level rather than a full concurrency strategy that handles concurrent update retries.

Pessimistic concurrency control relies on locking to prevent conflicts and this causes blocking and poor throughput under heavy concurrent write loads. Pessimistic locking can be appropriate for very high conflict cases but it is usually not the best fit for a high throughput payments service where locks would become a bottleneck.

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