What algorithm is illustrated by a rate-limiting snippet that uses a token bucket approach?

What algorithm is illustrated by a rate-limiting snippet that uses a token bucket approach?

• A. Leaky Bucket
• B. Token Bucket
• C. Sliding Window
• D. Counter

Answer: (B)

This tests understanding of rate-limiting using a token-based approach. In a token bucket model, tokens are added to a bucket at a fixed rate and the bucket has a maximum capacity. Each incoming request consumes one token; if a token is available, the request proceeds, and the token is removed. If no tokens remain, the request is delayed or rejected until tokens are replenished. This allows short bursts up to the bucket’s capacity while maintaining an average rate over time, which is exactly what a token bucket implementation demonstrates. The other options don’t fit as well. A leaky bucket enforces a steady, fixed output rate by leaking from a bucket at a constant pace, which doesn’t depend on having a pool of tokens. A sliding window tracks the number of requests in a moving time window rather than using a token pool. A simple counter just tallies requests and enforces a limit without modeling burstiness or token refilling.

This tests understanding of rate-limiting using a token-based approach. In a token bucket model, tokens are added to a bucket at a fixed rate and the bucket has a maximum capacity. Each incoming request consumes one token; if a token is available, the request proceeds, and the token is removed. If no tokens remain, the request is delayed or rejected until tokens are replenished. This allows short bursts up to the bucket’s capacity while maintaining an average rate over time, which is exactly what a token bucket implementation demonstrates.

The other options don’t fit as well. A leaky bucket enforces a steady, fixed output rate by leaking from a bucket at a constant pace, which doesn’t depend on having a pool of tokens. A sliding window tracks the number of requests in a moving time window rather than using a token pool. A simple counter just tallies requests and enforces a limit without modeling burstiness or token refilling.