Moving from a few hundred SMS messages to tens of thousands changes how an application should manage sending. The challenge is not simply calling an SMS API more often. You also need to control throughput, handle errors, track outcomes and prevent a temporary incident from blocking an entire campaign.
Before sending 100,000 SMS messages, prepare your processing architecture, monitoring and retry rules. Actual capacity depends on the API, configured limits, destinations and available routes; volume alone does not imply a guaranteed throughput.
1. Do not block your application on every message
A loop that sends messages one at a time and waits for every response can become slow and difficult to control. For larger campaigns, a queue separates campaign creation from execution.
The application records the messages to be sent, then workers process them progressively. This makes it possible to limit concurrent requests, pause processing and resume after an interruption.
The queue should retain the information needed to identify each message and its state. It should also make it possible to detect stuck jobs and retry them according to an explicit policy.
2. Respect rate limits
An API may impose request, concurrency or throughput limits. Additional limits may apply by account, destination or route.
Do not choose a concurrency level arbitrarily. Start with the documented limits for your account, run controlled tests and increase throughput gradually while monitoring errors and latency.
Plan how to slow down when the provider returns a rate-limit response. Continuing at the same rate after requests are rejected may make the problem worse.
3. Handle errors without creating duplicates
Not every error should trigger the same response. A temporary error may justify a retry; a validation error or invalid number generally requires correction rather than an immediate repeat.
Define error categories based on your API documentation. For temporary failures, use a limited number of retries and progressively longer delays. Keep a retry history so you can understand what happened.
Timeouts are particularly tricky: if your application receives no response, it may not know whether the request was processed. Do not blindly repeat the same operation without a deduplication strategy. If the API supports an idempotency key, use it; otherwise, design a mechanism that fits the provider’s capabilities.
4. Separate acceptance from delivery
A successful API response does not necessarily mean that the recipient received the message. Depending on the available features, you may need to track delivery reports or related events afterward.
At a minimum, store the message identifier returned by the API, the submission time, the request result and subsequent status updates. Do not mark a message as delivered unless you have a corresponding confirmation.
This distinction is essential for measuring campaign results and diagnosing gaps between submitted and delivered volume.
5. Monitor the campaign while it runs
A large campaign should not be launched and then left unattended. Monitor metrics such as:
- the number of queued messages;
- submission throughput;
- error responses and rate limiting;
- queue processing time;
- available delivery reports;
- application errors and callback failures.
Define alert thresholds and a procedure for pausing the campaign if errors exceed an acceptable level. Metrics should help distinguish an application issue from a provider-side or destination-specific problem.
6. Prepare for spikes and interruptions
Available throughput can vary by destination, time and routing conditions. Your application should be able to slow down without losing queued messages.
The queue should be persistent, workers should be able to restart and jobs should have a retry strategy. Test what happens if the application server restarts, the database becomes temporarily unavailable or the API stops responding.
Also provide manual pause and resume controls. For a sensitive campaign, being able to stop sending cleanly is just as important as being able to speed it up.
7. Protect data and prevent accidental sending
Before launch, review access to API keys, protect logs and avoid unnecessarily storing full message content or other personal data in them.
Start with a small, controlled recipient group. Verify variables, the number of messages created and error handling before releasing the full campaign.
For a 100,000-message campaign, a configuration mistake can have significant consequences. Validation checks, a volume estimate and explicit confirmation before launch are simple but useful safeguards.
8. A pre-launch checklist
Before submitting a large campaign, make sure you have:
- checked API limits and destination requirements;
- implemented a persistent queue;
- defined throughput and retry rules;
- planned deduplication to prevent duplicate sends;
- stored message identifiers and statuses;
- configured monitoring and alerts;
- tested with a small sample;
- prepared a pause and resume procedure.
In short: sending 100,000 SMS messages reliably is as much a software design challenge as an API-access question. A queue, disciplined error handling and suitable monitoring make campaigns easier to control and problems easier to diagnose.