Hi, I'm Abu Mercy
Crafting Resilient APIs & Elevating AI Data Integrity
Detail-oriented software engineer specializing in scalable Node.js architectures, secure authentication, fintech integrations, and rigorous AI model output evaluation for maximum precision and reliability.
About Me
Bridging scalable backend infrastructure with precision AI data engineering
I am a Backend Developer and AI Data Annotator with deep hands-on expertise in JavaScript, Node.js, Express, and structured data analysis.
My engineering background centers around designing robust RESTful APIs, implementing secure authentication and token authorization systems, managing relational (MySQL) and NoSQL (MongoDB) databases, and architecting fintech and webhook integrations for live platforms.
In parallel, I evaluate complex AI-generated outputs for factual precision, reasoning consistency, and safety guidelines at scale—ensuring high benchmark quality across language model pipelines.
📍 Location: Lagos, Nigeria • Available for Remote & Hybrid roles worldwide.
Backend & Business Systems
Building resilient REST APIs, Paystack payment gateways, recruitment ATS workflows, and database schemas optimized for reliability and low latency.
AI Output Evaluation & QA
Rigorous annotation, factual verification, and multi-turn prompt evaluation ensuring AI outputs meet stringent accuracy standards.
Security & Integrations
JWT session handling, password hashing, WhatsApp Business API automation, Paystack webhooks, and interactive Swagger/OpenAPI 3.0 documentation.
Technical Skills
Technologies, architectures, and methodologies I leverage daily
Languages & Frameworks
Databases & Modeling
API & Integrations
AI & Data Evaluation
Dev Tools & Version Control
Core Competencies
Work Experience
My professional track record across backend engineering and AI data pipelines
Backend Developer / Backend Team Member
- Built and integrated WhatsApp Business API functionality, including webhook handling, Phone Number ID configuration, and WABA integration.
- Implemented authentication and access token management for secure, automated business messaging.
- Developed scalable backend infrastructure and API integrations connecting WhatsApp business catalog features directly to core systems.
- Collaborated closely with cross-functional backend engineers on platform reliability, error logging, and continuous feature delivery for a live startup product.
Backend Developer
- Developed and maintained high-performance backend services and REST endpoints using Node.js and Express.
- Implemented secure user authentication and authorization systems with token-based access controls and encrypted credentials.
- Designed and integrated clean API interfaces with frontend client applications and third-party services.
- Ensured strict data accuracy, rigorous payload validation, and database schema consistency across internal systems.
- Conducted code reviews, debugged edge cases, and resolved production bugs to uphold high software reliability.
AI Data Annotator
- Evaluated multi-turn AI-generated responses for factual accuracy, safety adherence, and logical reasoning consistency.
- Followed rigorous annotation rubrics and guidelines to systematically label, grade, and review complex prompt datasets.
- Identified nuanced model hallucinations, syntactical bugs, and edge cases to enhance downstream model performance.
- Maintained exceptional benchmark quality scores while consistently meeting strict delivery deadlines.
- Adapted rapidly to evolving project requirements, multi-modal evaluation criteria, and QA standards.
Backend Projects
Production-grade APIs, fintech integrations, recruitment workflow systems, and transactional architectures
ATS (Applicant Tracking System) 👩🏽💻
A business-oriented backend architecture engineered for managing end-to-end recruitment operations, candidate evaluation stages, job listings, and recruiter workflows.
- Candidate & applicant lifecycle state machine
- Recruitment pipeline management with multi-stage evaluation
- Role-based access control for recruiters, interviewers & admins
- Designed for scalable enterprise talent acquisition workflows
Paystack Payment Integration 💳
Production-ready fintech backend integrating Paystack payment initialization, Dedicated Virtual Accounts (DVA), transaction verification, and secure callback/webhook handling.
- Automated payment initialization & checkout workflows
- Dedicated Virtual Account (DVA) payment processing
- Cryptographic webhook signature verification (HMAC-SHA512)
- Transaction verification and automated ledger reconciliation
CampusTrade API
A scalable e-commerce marketplace backend engineered with Node.js and MySQL via Sequelize ORM, powering student and vendor transactions.
- JWT-based authentication with bcrypt password hashing
- Email verification & secure password reset mechanisms
- Seller dashboard API with inventory management
- Interactive Swagger/OpenAPI documentation for client teams
Escrow Service
High-security transaction management system designed to safely hold buyer funds in escrow until all milestones or delivery criteria are satisfied.
- End-to-end buyer/seller transaction state machine
- Automated fund holding and release validation logic
- Dispute resolution workflows and immutable audit logs
- Webhook dispatchers for event-driven payment confirmation
BookStore API
Clean and documented RESTful web service for book catalogs, author metadata, inventory filtering, and stock updates.
- Full CRUD operations with strict parameter validation
- Category filtering, pagination, and sorting
- Comprehensive OpenAPI / Swagger 3.0 UI specification
- Graceful centralized error handling middleware
Pomodoro Tracker API
Productivity tracking and session analytics API built with Node.js and Express, enabling customizable focus intervals and metrics export.
- Focus block and break cycle state tracking
- Session duration calculation and historical logs
- Automated CSV data export functionality for personal analytics
- Lightweight and performant REST API endpoints
Volunteering
Empowering underserved communities through education and technology access
Umbrella for the African Child (U.T.A.C)
I am committed to creating positive social change by expanding access to opportunities through both community service and technology.
I participated in an impactful community outreach programme in Makoko, one of Nigeria's underserved communities, working alongside dedicated fellow volunteers to support educational initiatives, student mentorship, and community-focused activities.
Our collective efforts extend across multiple communities in Lagos and beyond, helping ensure youth and families have better access to vital learning resources, guidance, and future opportunity.
Let's Connect
Have an open backend role, an AI annotation project, or want to collaborate? Reach out directly.