Abdullah A.

I build secure, scalable backend systems and integrations that connect banks, payment platforms, and business applications. Over 12+ years I've designed and delivered mission-critical financial systems, from payment gateways and mobile banking to multi-country API platforms. I'm AWS certified (Solutions Architect, Developer, CloudOps) and WSO2 certified (API Manager and Micro Integrator). WHAT I CAN DO FOR YOU Backend Development - REST APIs and microservices with Java (Spring Boot, Hibernate) and Node.js - High-performance, secure services for banking, fintech, and enterprise systems - Database design and optimization: PostgreSQL, MySQL, MSSQL, Oracle System Integration & API Management - WSO2 API Manager, Micro Integrator, and Enterprise Integrator: setup, development, custom connectors, and performance tuning - API gateway migration (including Kong to WSO2 APIM) - REST, SOAP, and SOA integrations with third-party services, core banking, ERP, and CRM - Payment integrations: ISO 8583 (ATM, POS), card systems, fund transfer, bill pay, QR and NFC payments - SMS and messaging integrations via SMPP and API channels - API security: OAuth2, JWT, TLS and mutual TLS Full-Stack Web & Mobile - Web portals and dashboards with React and Node.js - Android app development, including mobile banking and agent banking apps Cloud & DevOps - AWS architecture and deployment (EC2, S3, IAM, API Gateway, Lambda) - Docker, Kubernetes, and Jenkins CI/CD pipelines - Monitoring and alerting with DataDog, Kibana, and Grafana HIGHLIGHTS - Lead integration and backend engineer for multi-country banking services at an international financial group, working fully remote since 2022 - Integrated ATM, POS, and web banking channels using ISO messaging, with TLS and mutual TLS for secure transmission - Built custom WSO2 connectors and fixed critical issues, improving CPU, memory, and latency performance across the integration platform - Architected a core payment gateway at a leading Bangladeshi bank, connecting core banking, agent banking, credit cards, and e-commerce for fund transfer, bill pay, top-up, and NFC/QR payments - Developed features for the Rocket mobile banking app, including QR merchant payments and e-KYC with live image detection and OCR - Built Android agent banking apps integrated with biometric fingerprint devices - Delivered a real-time online payment collection system with caching, recognized with an innovation award TECH STACK Java, Spring Boot, Hibernate, Node.js, React, Go, PHP, JavaScript, HTML5, CSS3, WSO2 APIM/MI/EI, REST, SOAP, ISO 8583, SMPP, OAuth2, JWT, mTLS, AWS, Docker, Kubernetes, Jenkins, Git, PostgreSQL, MySQL, MSSQL, Oracle, DataDog, Kibana, Grafana, JasperReports, Android CERTIFICATIONS - AWS Certified Solutions Architect – Associate - AWS Certified Developer – Associate - AWS Certified CloudOps Engineer – Associate - WSO2 Certified API Manager Developer – V4 - WSO2 Certified Micro Integrator Developer – V4 EDUCATION - Master of Information Technology, University of Dhaka - B.Sc. in Computer Science & Engineering, Patuakhali Science and Technology University - Published research in IEEE and IJSTR HOW I WORK - I start by understanding your system and goals, then propose a clear plan before writing code - Regular updates, clean code, and proper documentation handed over at the end - Security, stability, and performance first, especially for production and financial systems - Experienced with remote, international teams across different time zones - Available during Gulf business hours (GMT+6, only 2–3 hours ahead of UAE and Saudi Arabia) Whether you need a new backend or API, a complex system integration, a payment gateway connection, or a full-stack web application, send me a message with a short description of your project and I'll reply with how I'd approach it.