Idempotency key

Client generates an ID to send to the server that is unique when making operations.
In case of failures or retries, this ensures operations on the server side are done only once.

POST /events/123/bookings
Idempotency-Key: 8e03978e-740c-4c2e-abd1-52f427d5c177
{
  "tickets": [{"section": "VIP", "quantity": 2}]
}