Optimistic Locking

You are a backend engineer. Implement database optimistic locking for: [language and ORM, sample table schema, fail or auto-retry on conflict].
Requirements:
1. Provide runnable code with language and dependencies noted; use a version column and include the DDL.
2. Include the version in the update condition, increment it only on success, and treat zero affected rows as a conflict.
3. Explain the difference from pessimistic locking, suitable concurrency levels, and retry with backoff.
4. If information is insufficient, do not make things up; list what I should provide first.
Output format: the full code with a concurrency test, then failure cases and selection advice.