Sylex Assistant Pro
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Mobile AI Product Case Study

Sylex Assistant Pro

Sylex Assistant Pro is a multilingual voice AI assistant. Built with React Native, with full ownership of mobile development and UI/UX design. Available on Apple App Store and Google Play.

React Native TypeScript ASR + LLM + TTS i18next Apple App Store Google Play

1) Problem and Context

Why this project mattered
  • The legacy client had growing complexity and slower iteration speed for voice-first features.
  • Product requirements demanded stable multilingual support and clear voice-state UX across platforms.
  • The app needed stronger release-readiness for store distribution on both iOS and Android.

2) Solution Implemented

What was built

Mobile Architecture

Designed and built the React Native application in TypeScript with a clean modular structure, native platform integration, and maintainable voice-state management.

Voice Orchestration

Implemented end-to-end ASR to LLM to TTS orchestration with controlled request flow, state transitions, and resilient error handling for voice sessions.

UI/UX Design and Localization

Designed the full mobile UI/UX including voice-state flows, error states, and interaction feedback. Implemented automatic device-language detection and multilingual support using i18next across 7 locales.

Safety and Reliability

Enforced usage/session guardrails including request limits, session boundaries, and failure-safe messaging to improve product stability.

3) Technology Stack

Core tools
React Native TypeScript React Navigation i18next / react-i18next Jest ASR integration LLM orchestration TTS playback UI/UX Design

4) Impact and Outcomes

Production outcomes

Store Delivery

Shipped and maintained release-ready builds for Apple App Store and Google Play.

Maintainability

Improved code organization and developer workflow through a typed, modular React Native codebase.

User Experience

Delivered more consistent multilingual and voice-state behavior with clearer runtime feedback.

5) Challenges and Lessons

Engineering takeaways
  • Voice apps require strict state-machine design to avoid race conditions between listen, process, and speak phases.
  • Multilingual apps benefit from centralized translation keys and explicit fallback handling early in development.
  • Release success on mobile stores depends as much on build/release discipline as on core feature implementation.