5 exercises — practice the language for rate limits, quotas, burst limits, throttling, and tier upgrade communication.
0 / 5 completed
1 / 5
An API response includes this header: X-RateLimit-Remaining: 0.
A developer receives a 429 Too Many Requests response. What is the correct message to display to the user?
A 429 Too Many Requests response means the client has exceeded the rate limit — the maximum number of requests allowed in a time window. Good API communication tells users: (1) what happened (rate limit reached), (2) when they can retry (Retry-After header), and (3) what to do if they need more capacity (upgrade to a higher tier). A "service unavailable" message is incorrect — the service is available; the client is throttled.
2 / 5
Your API documentation states: "Free tier: 100 requests/day. If you exceed 100 requests, subsequent requests will be throttled."
What does throttled mean in this context?
Throttling in rate limiting means actively rejecting or delaying requests that exceed the defined quota. Most APIs return a 429 Too Many Requests response immediately (hard throttle). Some APIs use soft throttling: queueing requests and adding delay. The documentation "will be throttled" typically means "will receive 429 errors." Distinguish throttle (per-rate-period cap) from quota (total allocation over a longer period).
3 / 5
Complete the tier upgrade communication message:
"You're on the Free plan, which includes 500 API calls per month. You've used 490 of those. _____ to the Growth plan to get 50,000 calls per month and remove the burst limit."
"Upgrade" is the standard term for moving to a higher-value tier. "Upgrade" implies moving upward — more capacity, more features, higher cost. "Switch" is neutral (could be a lateral move or a downgrade). "Transfer" typically refers to moving data or accounts. "Apply" suggests a manual review process. In SaaS and API products, the call-to-action is almost always "Upgrade plan" or "Upgrade your plan."
4 / 5
An API product manager explains: "Our free tier has a rate limit of 10 req/sec, but we allow a burst of up to 50 req/sec for a maximum of 5 seconds."
What is a burst limit?
A burst limit allows clients to temporarily exceed the sustained rate limit to handle traffic spikes — common in real-world usage patterns where requests are not evenly distributed. After the burst window, the API throttles back to the base rate. This is implemented with token bucket or leaky bucket algorithms. Communicating this clearly in documentation prevents confusion: "You can burst to 50 req/sec, but your sustained rate is 10 req/sec."
5 / 5
Which sentence correctly uses the term quota in an API context?
Quota refers to a total allocation over a period (typically monthly or daily) — distinct from rate limit (requests per second/minute). A quota defines the ceiling over the billing period. When you exhaust your quota, you receive 429s until reset or upgrade. Quota communication typically includes: current usage, total quota, reset date, and an upgrade path. Option A misuses "quota" as a latency SLA — that would be "latency target" or "response time SLA."