Thread-Safe High-Traffic Rate Limiter | Dataford Interview Questions

Write a thread-safe rate limiter for an API endpoint that handles high traffic.

Implement allow_request(state, client_id, now, capacity, refill_rate), returning True when the client has a token and False otherwise. state is a shared dictionary, now is a nondecreasing timestamp in seconds, and refill_rate is tokens per second. The implementation must protect shared state during concurrent calls and avoid a single global lock bottleneck where practical.

Constraints

1 <= capacity
0 < refill_rate
client_id is hashable
now is a nondecreasing timestamp for each client
state is shared by all concurrent calls
The implementation must be safe under concurrent calls

Function Signature

def allow_request(state, client_id, now, capacity, refill_rate):

Your question is Thread-Safe High-Traffic Rate Limiter. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Write a thread-safe rate limiter for an API endpoint that handles high traffic.

Constraints

1 <= capacity
0 < refill_rate
client_id is hashable
now is a nondecreasing timestamp for each client
state is shared by all concurrent calls
The implementation must be safe under concurrent calls

Function Signature

def allow_request(state, client_id, now, capacity, refill_rate):

Your question is Thread-Safe High-Traffic Rate Limiter. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.