REST API or SMPP: from what monthly volume to switch to Morocco

However, when a business grows, volume increases. You go from a few thousand notifications to several million per month. During a "Black Friday" or the sending of a national communication, the REST API begins to show structural weaknesses (network latency, CPU overload, exceeding request limits).

It is then time to take an interest in the industrial telecoms protocol: SMPP (Short Message Peer-to-Peer). But when exactly should this time-consuming transition be made? Here is the tipping point.

The HTTP API (REST) ​​is based on a “Request/Response” model.
To send 1 SMS, you open a TCP connection (which takes milliseconds), you perform the SSL handshake (heavy cryptographic handshake), you send the HTTP Headers, the Payload, and wait for the response from the gateway.

Even using persistent HTTP connections (Keep-Alive), this process is "heavy".

• Technical limit: Often restricted by SMS providers between 10 and 50 Requests/Second (RPS) to protect against attacks.
• The glass ceiling: Beyond these numbers, you will encounter 429 Too Many Requests errors or timeouts, forcing you to create complex queues (Throttling).

(Note: The Bulk API gets around this by sending 1000 numbers in 1 HTTP request, but it doesn't solve latency if you're sending thousands of separate OTPs per second).

SMPP maintains a continuous binary connection (a TCP/IP tunnel) open 24/7 between your server and the SMS provider's firewall. There is no longer any overhead linked to SSL or HTTP Headers.

Advantages of SMPP:

1. Pure asynchronous: You send 500 SMS messages at once without waiting for a response from the gateway. She will answer you "later" in the same pipe.
2. Colossal throughput: throughput is negotiated route by route with the carrier (TPS); at EnvoiSMS, SMPP is offered on request to high-volume accounts.
3. Native Delivery Reports: No more need to manage complex HTTP webhooks. The Maroc Telecom network acknowledgment (IAM) goes directly into your open tunnel.

The major drawback:
Developing a robust SMPP client takes weeks, compared to hours for a REST API. You have to manage threads, silent TCP disconnections (Enquire Link), and low-level encoding (Data Coding Scheme) of Arabic characters in hexadecimal.

Here is the rule of the telecom industry adapted to the Moroccan market:

• Less than 500,000 SMS / month: Stay on the REST API. The API will largely cover your needs. Use Redis queues to smooth the load. The SMPP development cost will never be amortized.
• From 500,000 to 1 Million SMS / month (Gray Zone): The REST API is still capable of handling this load if you use "Bulk Endpoints" for marketing and reserve strict unit calls for OTPs.
• More than 1 Million SMS / month (The Tipping Point): This is where the SMPP comes into play. At this volume, hourly peaks will reach levels where HTTP latency slows down your databases. This is the essential architecture for banks, the telecom operators themselves, and e-commerce giants (Jumia, Marjane).

If you've reached this tipping point, don't cut off the REST API overnight. The migration is done in 3 “Shadow IT” phases:

1. RX (Receiver) implementation: First, configure your SMPP client only to “listen” (Receiver mode). Ask your provider to route DLRs to this new connection instead of the old HTTP webhooks.
2. Partial TX implementation (Transmitter): Transmit 5% of your marketing campaigns via SMPP (without impact if it crashes), while keeping the REST API for your vital OTP sendings.
3. Full switchover (TRX): Once the stability of the TCP client has been proven over several days (correct management of network reconnections), switch over all transactional and marketing routing. The old REST API will become your fallback plan in the event of a low-level infrastructure crash.