SMS API Rate Limits: How to Build a Stable Polling Loop
SMS API rate limits polling loops are a common source of broken verification integrations. A loop that polls too fast gets throttled, and one that polls too slowly leaves users waiting. Getting the balance right keeps your OTP flow stable and your API usage within limits.
Direct answer: Respect the API's published rate limits, add exponential backoff on errors, cache responses, and poll only while a code is expected. A stable polling loop uses a sensible interval, stops after a timeout, and handles 429 and 5xx responses by waiting longer instead of retrying immediately.
Why rate limits exist
Rate limits protect the API from overload, prevent abuse, and keep performance fair for all users. They are usually expressed as requests per second, minute, or day. Exceeding them returns an error, often HTTP 429, and repeated violations can lead to temporary blocks.
Designing a stable polling loop
- Read the limits. Check the API documentation for exact thresholds before writing code.
- Choose an interval. Poll every few seconds, not in a tight loop.
- Add a timeout. Stop polling after a set period and inform the user.
- Handle 429 responses. Wait and retry with exponential backoff.
- Handle 5xx errors. Retry a limited number of times with increasing delays.
- Stop on success. Cancel the loop once the code arrives or the user leaves the screen.
Exponential backoff explained
Exponential backoff increases the wait time after each failure. For example, wait two seconds, then four, then eight, up to a cap. Add random jitter to avoid many clients retrying at the same moment. This pattern keeps your integration polite and reduces the chance of a longer block.
Polling vs webhooks
Polling asks the API repeatedly whether a message arrived. Webhooks push the message to your server when it is ready. Webhooks are more efficient and avoid rate-limit problems, but they require a public endpoint and signature verification. Many teams use webhooks as the primary method and polling as a fallback.
The OtpGet API documentation explains endpoints and delivery events you can use for both approaches.
Practical limits to watch
- Requests per second on activation endpoints
- Concurrent numbers per account
- Daily message and lookup quotas
- Burst limits during peak hours
Testing your loop
Use a staging environment and a test number to simulate slow delivery and errors. Verify that your loop backs off, respects limits, and stops on success. Log response codes and timings so you can spot problems before they reach production.
You can get test numbers from OtpGet to validate your polling logic.
Frequently Asked Questions
What are SMS API rate limits?
They are caps on how many requests you can make in a period. Exceeding them returns errors and may trigger temporary blocks.
How often should I poll for an OTP?
Every few seconds with a timeout is reasonable. Avoid tight loops, and back off when you receive errors.
Should I use webhooks instead of polling?
Webhooks are more efficient and avoid rate-limit issues, but polling is a useful fallback when webhooks are not available.
What does HTTP 429 mean?
It means you exceeded a rate limit. Wait and retry with exponential backoff instead of retrying immediately.
Conclusion
SMS API rate limits polling loops work best with a slow interval, a timeout, and backoff on errors. Respect the published limits, prefer webhooks where possible, and test your logic before production. Read the OtpGet API docs and build a loop that stays stable under pressure.
Related reading: more API tutorials on the OtpGet blog.