The product SmsApp rents virtual phone

The product

SmsApp rents virtual phone numbers so people can receive a one-time verification code for WhatsApp, Telegram, Gmail and 150+ other services, or keep a number for a month. Customers top up a prepaid wallet, and resellers automate everything through a REST API.

My role

Lead developer since February 2026. My first big change was moving the backend from Firestore to MySQL. Since then I've written about 99% of the code changes.

What I built

A prepaid wallet that can't go negative, with refunds paid exactly once

Automatic refunds when no code arrives, safe across crashes

Card and two crypto payment providers with verified webhooks

Fraud controls: 3-D Secure checks, card holds, shared-IP bans and chargeback tracking

Supplier routing by delivery rate, price and stock, with failing suppliers switched off automatically

Monthly rentals, shared numbers and a receive-only email inbox per rental

Pre-rendered SEO pages in 24 languages, including right-to-left Arabic and Hebrew

Hard problems

Payments you can't fake: one provider's callbacks are unsigned, so they are only a hint and are re-checked against the provider's API before any credit

Background jobs that can't double-pay: the refund job uses a lock that frees itself if a run hangs, and every refund is claimed atomically

Results

24 interface languages

Numbers in 150+ countries

4,700+ pages in its 24 language sitemaps

4,000+ automated tests across server, web and mobile