Overview

Digital wallets (eSewa, Khalti) are Nepal’s payment backbone for e‑commerce. This case highlights architectural patterns enabling reliable payments on mobile networks with variable latency and coverage.

Key Architecture Themes

  • API‑first: REST/JSON endpoints for payments, balance, and billers; idempotent operations; webhook callbacks.
  • Mobile UX resilience: Offline states, retries, cached menus, and clear error surfaces to reduce drop‑offs.
  • Security layers: Tokenization, device binding, OTP flows; rate limiting and anomaly detection.
  • Integration ecosystem: Merchant SDKs (web/app), QR rails (Fonepay), and settlement cycles with banks.

Outcomes

  • Widespread merchant adoption; payments embedded into checkout, utility, and ticketing flows.
  • Higher conversion vs. cards; improved customer trust with transparent states.

Lessons (Unit 3 lens)

  • Reliability is a product feature—network variability must be handled in client + server.
  • Clear API contracts and idempotency keys prevent double‑charges and support retries.
  • Observability (logs, traces, alerts) is essential for payment SLOs.

Chapters covered

  • Internet & web infrastructure (3.1–3.3)
  • Mobile platforms and app patterns (3.5)