TP is the highest-stakes message most businesses send. It is on the critical path of a login or a checkout — if it is slow or missing, the user is stuck at a screen they cannot pass. Yet OTP is frequently treated as a fire-and-forget SMS. The teams with the best conversion treat it as a latency-sensitive, multi-channel, instrumented system. Here is what that looks like.
Latency is a conversion metric
Industry data and our own routing telemetry agree: completion rates fall measurably once OTP delivery passes roughly thirty seconds, and fall sharply past sixty. Users assume failure, request a resend, switch channels, or abandon entirely. Treat end-to-end OTP latency — submission to handset — as a product KPI, alarmed and dashboarded, not as an afterthought.
Route for speed, not just for price
- Use direct operator routes for OTP. Grey and wholesale routes add hops, queuing, and unpredictable jitter.
- Prefer SMPP for submission to remove per-message TLS handshake latency from the critical path.
- Maintain per-operator latency baselines and rotate away from any route whose p95 delivery time degrades.
- Do not let bulk marketing traffic and OTP traffic share the same bind or queue — give OTP a dedicated, prioritised path.
Build a fallback chain
No single channel delivers to every user every time. A resilient OTP flow tries the fastest appropriate channel first and escalates: WhatsApp authentication template or RCS if the user is reachable there, SMS as the universal fallback, and a voice OTP (a call that reads the code aloud) as the last resort — voice is invaluable for accessibility and for the small fraction of users on whom SMS reliably fails. The escalation should be automatic and time-boxed, not a manual 'try again' the user has to trigger.
Reduce the friction around the code itself
- Use the SMS Retriever API on Android and the autofill domain-binding format on iOS so the code populates automatically — every manual keystroke removed is conversion saved.
- Keep codes short. Six digits is standard; eight is rarely worth the extra friction.
- Make the message template unambiguous and consistent so password managers and OS autofill recognise it.
- Set a sane expiry — long enough to survive a slow delivery, short enough to limit replay risk. Five to ten minutes is typical.
Instrument the whole funnel
Measure four numbers per channel and per operator: submission success, delivery rate, delivery latency (p50/p95), and — the one that actually matters — verification completion. A 99% delivery rate paired with a 70% completion rate tells you the message is arriving but arriving too slowly, or the UX around code entry is broken. Delivery without completion is not success.
BroadNet's Verify API handles channel selection, the fallback chain, code generation, and expiry, and exposes per-channel completion analytics — so you optimise OTP on the metric that matters instead of guessing.
A note on cost
OTP is where the temptation to chase the cheapest route is strongest and most damaging. The cost difference between a premium direct route and a grey route is a fraction of a cent. The cost of a failed login is a user who may not come back. For OTP specifically, optimise for delivery and speed first; treat unit price as the last consideration, not the first.