Manage GPU Credits with Expiration

##### Question Implement a GPU credit manager supporting out-of-order operations: API add_credit(id, amount, timestamp, expiration) // adds ‘amount’ credits usable in [timestamp, timestamp+expiration) charge(amount, timestamp) // consume ‘amount’ credits at ‘timestamp’; always draw from credits that expire soonest first (tie-break by any order) get_balance(timestamp) // return total unexpired credits available at ‘timestamp’ ##### Constraints add_credit and charge calls may arrive in arbitrary time order charge(…) must fail silently or partially apply only if enough total balance exists at that moment Design an efficient data structure to support ~10^5 operations with O(log n) per call.