Concurrency

Race Conditions & Semaphores : Handling 500+ Concurrent Users

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A technical diagram titled "Anatomy of a Race Condition" showing two threads (User A and User B) simultaneously accessing a marketplace database with 1 coupon available. Both threads read the value '1', pass the check, and write back '0', resulting in two coupons being issued for a single stock item, illustrating a financial loss scenario due to a lack of synchronization.

1. The Core Problem: How Does a Race Condition Occur? Imagine you have exactly 50 discount coupons left in your database. When a user clicks “Apply,” the backend server typically executes code in three steps: Read: Check the database for remaining coupons. (e.g., Coupons = 50) Check: Are the remaining coupons > 0? If yes, … Read more