Sazzadur Rahman

Software Engineer(MERN)

Codebase Technologies • Full-time

Aug 2025 - Present • 9 mos

Core Stack: Next.js, React Native, Expo, NestJS, Express.js, TypeScript, PostgreSQL. Professional Overview: During my tenure at Codebase Technologies, I contributed to the development of enterprise-grade digital banking solutions and fintech platforms. My role focused on architecting a unified experience across web and mobile, supported by high-performance, secure backend services. Web & Frontend: Developed SEO-optimized, lightning-fast web interfaces using Next.js. Implemented Server-Side Rendering (SSR) and Static Site Generation (SSG) to ensure peak performance for complex banking dashboards and portals. Mobile Development: Engineered cross-platform mobile applications using React Native and Expo. Managed the full mobile lifecycle from prototyping to deployment, ensuring a native-like experience on both iOS and Android. Backend Architecture: Built modular and highly testable server-side applications using NestJS. Leveraged Express.js for lightweight microservices and high-speed middleware integrations. Fintech Integration: Integrated secure Open Banking APIs, multi-currency payment gateways, and robust authentication layers using OAuth2, JWT, and Passport.js. Key Achievements: Unified Ecosystem: Successfully synchronized core business logic between the Next.js web platform and React Native mobile app, reducing code redundancy by 30%. Performance Engineering: Optimized Next.js bundle sizes and image assets, leading to a 40% improvement in initial page load speeds. Scalable Microservices: Designed a microservices-ready architecture with NestJS, capable of handling thousands of concurrent financial transactions with 99.9% reliability. Rapid Delivery: Utilized Expo’s managed workflow to accelerate the mobile app development and testing cycle.

Software Engineer

bdCalling • Full-time

Feb 2024 - Aug 2025 • 1 yr 6 mos

Tech Stack: NestJS, Express.js, Fastify, PostgreSQL, Prisma, TypeORM, Socket.io, WebRTC, Redis, BullMQ. Description: As a Backend Engineer at bdCalling, I specialized in building high-performance, modular, and real-time server-side applications. I focused on architecting secure systems and integrating advanced communication and payment features for global clients. Framework Mastery: Expertly utilized NestJS for structured architecture, while leveraging Express.js for flexible middleware-based APIs and Fastify for ultra-low overhead, high-performance microservices. Database Management: Managed complex relational data using PostgreSQL, optimizing schema design and migrations through Prisma and TypeORM. Real-Time & Media: Developed real-time communication engines using Socket.io and implemented peer-to-peer streaming with WebRTC. Global Payments: Integrated multi-platform payment gateways including Stripe, PayPal, Google Pay, and Apple Pay to ensure secure financial transactions. Security & Cloud: Implemented enterprise-grade security with JWT, OAuth2, and Passport.js. Managed file storage via AWS S3 and handled full application deployment on VPS environments with Push Notifications. Key Achievements: Performance Boost: Optimized backend performance by migrating critical high-traffic routes to Fastify, reducing latency by 20%. Scalable Data: Designed and optimized PostgreSQL queries, improving data retrieval speed for large datasets by 25%. Real-Time Success: Built a robust notification and live-chat system supporting thousands of concurrent users without performance degradation. Deployment Excellence: Streamlined VPS deployment workflows, ensuring 99.9% uptime for client-facing production environments.

Software Engineer

SoftServe • Full-time

Dec 2022 - Aug 2023 • 8 mos

Tech Stack: Angular, Angular Material, Node.js, NestJS, Express.js, TypeScript. Professional Overview Developed and maintained enterprise-scale web applications by bridging the gap between sophisticated frontend interfaces and scalable backend architectures. Focused on delivering modular, high-performance solutions within a fast-paced agile environment. Frontend: Built complex Single Page Applications (SPAs) using Angular and utilized Angular Material to deliver accessible, responsive, and high-quality UI components. Backend: Engineered robust server-side logic and modular services using NestJS and Express.js, ensuring secure and efficient data processing. State Management: Optimized data flow and handled complex asynchronous workflows using RxJS and reactive programming patterns. Key Achievements System Migration: Led the transition of legacy modules to NestJS, improving code maintainability and team development velocity by 30%. Development Efficiency: Developed a library of reusable Angular Material components, reducing frontend development time for new features by 20%. Performance Optimization: Enhanced application responsiveness and reduced initial load times by implementing Lazy Loading and efficient Change Detection strategies. Scalable Architecture: Designed a highly modular backend architecture that successfully supported a significant increase in concurrent user traffic without compromising stability. Quality Engineering: Maintained high code standards by adhering to SOLID principles and ensuring high test coverage across critical application modules.