Key Takeaways
- Appointment businesses die on two clocks: portal OTP and same-day reminders. OTP must win the device queue.
- Marketing “book this week” SMS is a third lane. It cannot sit in front of login codes.
- Priority queues fail when one Android is the whole stack. Free is one device — do not enable promo on it.
- Raise OEM/Android rate ceilings carefully; carrier fair-use still applies. Never title this “Unlimited SMS.”
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free: 1 device / 300 SMS lifetime / 300 contacts. Developer: 25,000 SMS per year.
Android SMS gateway scenario 960 is a salon, dental desk, or tutoring shop whose customers log into a booking portal and also expect a same-morning “we still have you at 10:30.” Both are SMS. Only one can be first on a single radio. Priority is a written queue rank, not a Slack hope.
Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Developer Center. Carrier pacing is still the MNO — GSMA.
Priority is a queue, not a hope
Your worker should dequeue portal OTP before T-2 reminders, and T-2 before T-24, and never dequeue a campaign on the OTP device. If the booking engine and the CRM marketing tool both POST to the same Android, you do not have a priority queue — you have a stampede.
A 08:05 reminder wave that delays 08:06 login codes will empty the chair and lock the portal in the same fifteen minutes.
OTP, same-day, promo
| Rank | Message | Device | Late policy |
|---|---|---|---|
| 1 | Portal / app OTP | Dedicated | Expire in app; do not pile retries blindly |
| 2 | Same-day reminder | Second SIM or after OTP drain | Skip if appointment already started |
| 3 | T-24 reminder | Same as 2 | Idempotent on appointment id |
| — | Promo / win-back | Other MSISDN | STOP; quiet hours |
Devices on plan: Starter 2, Professional 5, Business 15.
How reminders starve login
Concatenated Unicode templates turn “short” reminders into two parts. A 200-row morning CSV is not 200 SMS on the radio. OTP waits behind parts you did not count. Parts and retries.
Portal login vs chair-time
Idempotency: appointment id + reminder kind. Cancel in the booking tool must cancel the hold. Numbers from the PMS in E.164 — front-desk retyping is how the wrong patient gets the slot.
REST from the booking app — PHP, C#. Not SDKs. MCP is a REST wrapper.
Radio pace and OEM ceilings
You can raise Android/OEM SMS rate ceilings. Carrier fair-use and plan caps still apply. Do not write tutorials titled as if operator limits disappear. OEM background.
Plan fit for a salon or clinic desk
Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free (300 lifetime) is a canary, not Monday volume. Developer is 25,000 SMS per year. Paid tiers uncap platform volume; you still buy devices and airtime. Pricing.
Monday 08:00
Canary staff OTP, then one reminder, then watch queue depth. Spare charged OTP phone. Name who tops up prepaid before the first holiday week. Doze exemptions on both devices.
Codes and no-show lists
Do not log full OTP. No-show win-back is marketing — consent and STOP. Rotate keys. Not a CodeCanyon clinic pack.
One phone on Free
If you only have 1 device, send OTP only. Reminders wait until a second handset is on a paid device slot. CPaaS if you refuse phones.
Checklist
- Queue rank written and enforced in the worker.
- Promo cannot POST to the OTP device.
- Same-day reminders skip once the slot started.
- Idempotency on appointment id.
- Staff canary before Monday open.
- Airtime + spare OTP phone funded.
Next steps
Put 20 OTP and 200 reminders in a staging worker; prove OTP latency stays flat. API · Docs.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- OTP and 2FA SMS on AndroidAuthentication flows
- multi-device and dual SIM routingCapacity and failover
- SMS delivery reports (DLR)Delivery status tracking
- SMS API documentationLive endpoint reference
