store: postgres
POST /payments  key=k-1            -> HTTP 201  replayed=-    retry-after=-    {"id":1,"customer":"cus_42","amount":1999,"currency":"INR"}
POST /payments  key=k-1 (retry)    -> HTTP 201  replayed=true retry-after=-    {"id":1,"customer":"cus_42","amount":1999,"currency":"INR"}
payments in the table: 1
what the store holds: row status COMPLETED, response_status 201