gimesha.dev
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Case Study

Building Resilient Mobile Payment Flows

Kotlin · Jetpack Compose · Retrofit · Coroutines · Material 3

Executive Summary

Built wallet features (card reloads, QR payments, bill-pay). A clean Retrofit API layer and resilient UI reduced visible errors and clarified flows.

The Problem

  • Payment flows were overly coupled to banking onboarding.
  • Intermittent network caused confusing failures and abandons.

Architecture & Approach

  • 1
    Feature-based packages (screens, view models, DI)
  • 2
    Retrofit interfaces with clean DTOs, interceptors, consistent error envelopes
  • 3
    Compose UI with unified components (cards, inputs, buttons) and a11y labels
  • 4
    Robust retries and offline affordances where possible

Challenges & Trade-offs

Gateway sandbox limitations → emulated webhooks + idempotent retries in dev

UI complexity → extracted shared components to keep code tidy and reusable

Outcomes & Results

  • Fewer user-visible errors in payment flows via defensive UI and API handling
  • Faster iteration thanks to a clean, testable Retrofit layer