Android SMS Gateway Scenario 940: Edtech multi-device failover in practice

Android SMS gateway scenario 940 is an exam-platform team that already sends student login OTP from Android SIMs. Midterm Monday, one handset Dozes or a prepaid pack dies. Failover is not “we have another phone somewhere.” It is a warm second radio the worker can select before the first paper starts.

Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Developer Center. Industry messaging context: GSMA. Not a CodeCanyon campus pack.

Exam week is a failover drill

Capacity planning starts the week before the window, not when the LMS graphs go red. Count peak OTP per 15 minutes, add retry rate, then decide if one radio can finish a burst before the next login wave. If not, you need two live devices in the OTP pool — plus a spare if one drops.

A spare that last paired in March will miss the 09:00 paper. Failover is a yesterday canary, not an asset tag.

Multi-device · API.

Proctor OTP vs parent alerts

Device meters: Starter 2, Professional 5, Business 15. Exam week usually hits the device cap first.

Warm spare, not a drawer phone

Same OEM exemptions, charger, locked user, and pairing as production. After any SIM swap, re-canary. Dual SIM on one handset is operator diversity, not two campuses. Dual SIM.

Health check then cut

Worker rules: last successful send, last DLR, battery, pairing heartbeat. If primary fails, pin new OTP to the spare device id. Do not spray the same code to both SIMs. Idempotency stays on the login attempt id.

REST — PHP, C#. Not SDKs. Live fields in Developer Center.

Semester start vs midterm

Enrolment week is a different shape (many new numbers, messy E.164). Midterms are returning users and a sharp OTP spike. Plan SIMs and airtime for both. Raise OEM rate ceilings carefully; carrier fair-use still applies.

Devices before volume

Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free is 300 SMS lifetime on 1 device — enough to prove pairing, not an exam window. Developer: 25,000 SMS per year. Starter / Pro / Business uncap platform volume; you still buy handsets and operator credit. Pause on Free/Developer at allowance. Pricing.

Invigilator night

Name who watches pairing from 06:00. Canary staff numbers at 21:00 the night before. Doze exemptions after OEM updates. Setup · Doze.

Student PII and keys

Do not log full OTP. Rotate keys when a contractor leaves. Parent promo STOP is not a student-account delete.

When one campus SIM is enough

A 40-student pilot can live on one radio. A national exam window cannot. If you refuse device ops, that lane is CPaaS. vs aggregator.

Checklist

• OTP pool ≠ parent promo pool.
• Spare paired, charged, canaried in 24h.
• Cutover rule uses health, not tickets.
• Idempotency on login attempt id.
• Airtime on both SIMs; top-up owner named.
• Peak OTP/15m written before the window.

Next steps

Kill pairing on primary in staging, prove OTP continues on spare. Downloads · API docs.