Manage rate-limiting of your SMS API during traffic peaks (Ramadan, Black Friday)

It is at this point that unprepared developers encounter the “Rate Limiting” wall. The API sends back ‘HTTP 429 Too Many Requests’ errors, your expectation file explodes, and the vital messages do not arrive.

Here’s how to anticipate and manage these extreme traffic peaks on Moroccan telecom infrastructure.

Rate-Limiting is not a bug, it is a vital network protection.

1. Application Rate-Limiting (Your API Provider): The API limits each key to a certain rate (at EnvoiSMS: 60 to 1,200 requests per minute depending on the plan) to prevent a single client from monopolizing the database.
2. The Throttling Network (the Moroccan Operators): Moroccan Telecom, Orange and inwi allocate a specific bandwidth (TPS) to each gateway. During Ramadan, voice and P2P SMS traffic (between people) explodes.

If you try to force the passage by sending thousands of SMS at once at 5 p.m., on the eve of Eid, you will not only be blocked by the API (HTTP 429), but the few accepted messages will be placed in [Pending] (/fr/blog/dlr-pending-delivered-failed-unknown-which-means-truly-these/) for hours.

Do not discover your limit on day J. Ask your technical team to validate these two points 30 days before the peak:

1. Check your theoretical rate limit: What is the requests-per-minute limit on your production API key? If your customer base has grown from 50,000 to 300,000 in one year, your technical plan may not be more suitable.
2. Move to Bulk Mode: If your code makes a HTTP loop (1 SMS = 1 HTTP Request), you have no chance.You must use the API /v1/messages/bulk endpoint (up to 10,000 messages per request).Instead of making 1000 SMS requests, you make 1 single HTTP request containing a JSON of 1000 numbers.

The winning strategy in Morocco is not to send as quickly as possible, but as intelligently as possible.

Never mix streams: During a peak, the worst nightmare is that your marketing campaigns block your transaction SMS (e.g. the customer receives the Black Friday promotion but the double-authentication SMS to finalize the payment takes 10 minutes to arrive). - Solution: Use two different connections/API keys.

The Timeline: Never schedule a campaign of 500,000 contacts "at noon pile". - Cut your list (Sharding) into geographical or behavioral lots. - Inject lots into the API gradually (e.g.: 20% at 10 p.m., 30% at 12 p.m., 50% at 15 p.m.). - Spreading the load, the Moroccan operator will process your SMS through the water, and your delivery rate will be optimal.

What if error 429 falls in the middle of the biggest campaign of the year?

Your code should not panic. It should use the Exponential Backoff algorithm: 1. If the API returns 429, the system will fall asleep (Sleep) for 5 seconds. 2. It will ring. If it still fails, it will fall asleep for 10 seconds. 3. In the meantime, it will send an automatic alert (Slack/Email) to your DevOps to notify you that the network ceiling has been reached. 4. Unsended messages remain securely stored in your Local waiting line (Redis) and are not lost.

Software anticipation is the only guarantee of technical success during consumer peaks in Morocco.A promotional SMS that arrives at 3am because it was blocked will generate more complaints to the CNDP than sales.