Race Conditions Prompts

My [web app / API / backend] has a feature where users can [redeem a coupon / claim a reward / reserve a seat / purchase a limited item]. Right now, if two users hit this at the same time, they can both succeed even though only one should.

Handle race conditions for this feature:
- Use locks or atomic database operations so only one request can read-check-write at a time
- If a second request arrives while the first is processing, it should wait or get a clean "not available" response
- Make sure the fix works under real traffic, not just single-user testing
- Add clear error messages when a resource is no longer available

My stack: [your language and framework here, e.g. Node + PostgreSQL, Python + Django, Ruby on Rails]

I'm learning, so explain each part simply.

I want to test whether my [feature, e.g. token redemption / inventory checkout / balance deduction] is vulnerable to race conditions before I launch.

Build a simple test script or admin tool that:
- Simulates [10-50] users hitting the same [endpoint / action] at the exact same time
- Targets a shared resource like [a coupon with 1 use left / an item with limited stock / a user balance]
- Logs the result of every request (success or failure)
- Checks the final database state against what it should be (e.g. balance should never go negative, stock should never go below zero)
- Clearly reports if the race condition was triggered

My stack: [your language and framework here]

I'm learning, so explain each part simply.

My [app] has a critical action where [describe action, e.g. users withdraw from a shared pool / admins approve payouts / players trade items]. Database locks alone aren't enough because the logic spans multiple steps.

Set up a queue-based system that:
- Accepts incoming requests immediately and returns "processing" to the user
- Processes them one at a time (or in safe batches) in order
- Updates the shared resource only inside the queue worker, never from direct API calls
- Notifies the user when their request is complete or rejected
- Handles failures gracefully (retry or refund)

My stack: [your language and framework here]

I'm learning, so explain each part simply.