Senior Full Stack Developer and Optimization Engineer

We are looking for a highly experienced Senior Full-Stack Performance & Optimization Engineer to take ownership of the performance, scalability, code quality, and technical optimization of the WonnPay application.

This role is ideal for an engineer who can go deep into an existing production codebase, identify bottlenecks across Frontend, Backend, APIs, databases, networking, and infrastructure, and turn the application into a significantly faster, cleaner, and more scalable platform.

Key Responsibilities:

Application Performance

• Analyze and improve overall WonnPay app performance and responsiveness.
• Identify performance bottlenecks across mobile, frontend, backend, APIs, database, and infrastructure.
• Reduce app startup time, screen loading time, API response time, and transaction processing latency.
• Optimize critical user journeys including login, KYC, wallet, deposits, withdrawals, card management, and transactions.
• Establish performance benchmarks and continuously measure improvements.

Frontend / Mobile Optimization

• Review and optimize the existing frontend/mobile architecture and codebase.
• Improve React Native / Expo application performance.
• Optimize rendering, navigation, state management, memory usage, and network requests.
• Remove unnecessary API calls, duplicate requests, inefficient components, and unnecessary re-renders.
• Implement appropriate caching, lazy loading, pagination, and optimized data-fetching strategies.
• Improve application stability, crash rates, and overall user experience.

Backend & API Optimization

• Review and refactor existing backend services and APIs.
• Identify slow endpoints and reduce API latency.
• Optimize Node.js / TypeScript services and asynchronous processing.
• Eliminate unnecessary service-to-service calls and inefficient workflows.
• Improve API architecture, error handling, concurrency, and scalability.
• Optimize database queries, indexing, connection handling, and data access patterns.
• Introduce caching and other performance mechanisms where appropriate

App Architecture & Code Quality

• Conduct a full technical performance assessment of the existing WonnPay codebase.
• Identify duplicated, inefficient, outdated, or poorly structured code.
• Refactor FE and BE components without disrupting production functionality.
• Establish clean coding standards and reusable architectural patterns.
• Identify technical debt and create a prioritized optimization roadmap.
• Work closely with Engineering, Product, QA, DevOps, and Security teams.

Monitoring & Observability

• Implement or improve application performance monitoring and observability.
• Track API latency, error rates, crashes, resource utilization, and critical transaction performance.
• Establish meaningful performance KPIs and SLAs/SLOs.
• Use profiling, logs, traces, metrics, and real-user performance data to identify issues.
• Continuously monitor production performance and proactively resolve bottlenecks.

Required Technical Skills:

• 6+ years of professional software engineering experience.
• Strong Full-Stack development experience.
• Strong experience with React Native / Expo or equivalent mobile technologies.
• Strong Node.js / TypeScript experience.
• Strong understanding of REST APIs and distributed systems.
• Strong SQL/database optimization experience.
• Experience with PostgreSQL or similar relational databases.
• Experience with Redis/caching technologies.
• Strong understanding of cloud infrastructure such as AWS or Azure.
• Experience with application profiling and performance optimization.
• Strong understanding of asynchronous programming, concurrency, networking, and API architecture.
• Experience working with production fintech, payments, Web3, or high-transaction applications is highly desirable.

What We Are Looking For:

We are not looking for someone who only develops new features.

We need an engineer who can take ownership of an existing production platform, investigate why things are slow, identify the root causes, and make measurable improvements across the entire technology stack.