Race Conditions in Production: When Two Requests Compete for One Resource

𝐒𝐨𝐟𝐢𝐚 𝐢𝐬 𝐢𝐧 𝐌𝐚𝐝𝐫𝐢𝐝. 𝐉𝐚𝐦𝐞𝐬 𝐢𝐬 𝐢𝐧 𝐓𝐨𝐫𝐨𝐧𝐭𝐨.

Both find the same small hotel in Lisbon for the same weekend. Both see “Only 1 room left!”

At exactly the same second, both tap “Book now.”

Who gets the room?

In a badly built system, both do. Two confirmations. One room. One very awkward morning at the front desk.

Engineers call this a race condition: two operations each make a decision on information that’s about to become wrong.

Exactly the same scenario plays out in payments, just with money instead of rooms. Two withdrawals, one balance, same moment.

Which of the five fixes have you used in production?