JOSIAH ONYEJE
Technical Mentor/Coding Instructor at Self-Employed
About
Experience
Technical Mentor/Coding Instructor
Self-Employed
January 2026 - Present
- Provide 1-on-1 mentoring and code review for developers learning .NET/C#, covering backend fundamentals, API design, and career readiness. - Deliver structured career guidance and mock technical interviews to help mentees prepare for backend engineering roles.
Backend Software Engineer (.NET)
Suntrust Bank
August 2024 - June 2026
- Designed and built ASP.NET Core Web APIs for core banking workflows, applying SOLID principles, Clean Architecture, and established design patterns to keep services testable and maintainable as the codebase grew. - Wrote and tuned SQL queries and stored procedures supporting high-volume financial transaction processing, improving query performance on production banking workloads. - Owned backend services supporting secure financial transaction flows, working alongside the bank's compliance and risk requirements for handling sensitive customer and transaction data. - Partnered with frontend engineers (HTML, CSS, JavaScript, React) to deliver end-to-end banking features, translating product requirements into clean API contracts. - Operated inside Agile sprints with Git-based workflows, contributing to a consistent release cadence for customer-facing banking applications. - Applied object-oriented design and refactoring to legacy areas of the codebase, reducing duplication and improving long-term maintainability.
Independent Backend Software Engineer (Freelance, Part-Time)
Self-Employed
January 2023 - Present
- Designed and shipped production fintech backend systems for independent clients, including interbank payment processing, virtual card middleware, and identity verification services. - Designed normalized database schemas and optimized SQL queries across SQL Server and PostgreSQL projects to support reliable, high-performance business applications. - Deployed services to Render with publicly accessible Swagger/OpenAPI documentation, enabling clients and collaborators to test and validate APIs independently. - Built responsive front-end interfaces (HTML, CSS, JavaScript) where needed to deliver complete, demo-ready solutions rather than backend-only deliverables. - Ran client discovery directly, gathering requirements, scoping technical approach, and managing delivery against business goals.
Education
Bachelor (B.Sc)
National Open University of Nigeria (NOUN)
January 2022 - August 2026
Field: Information Technology
Higher National Diploma (HND)
Federal Polytechnic Nasarawa
January 2020 - August 2022
Field: Mechanical Engineering
National Diploma (ND)
Federal Polytechnic Nasarawa
January 2018 - August 2019
Field: Mechanical Engineering
Skills
Advanced
Intermediate
Projects
CoralPay Interbank Transaction Processing System
January 2023
Engineered a secure payment-inflow platform for interbank fund transfers, implementing PGP encryption/decryption and digital signature verification to meet financial security standards.
Virtual Card Middleware (Interswitch Integration)
January 2023
Built a secure backend integrating Interswitch APIs for full card lifecycle management: creation, activation, PIN reset, and transaction queries.
School Management System (Live Public API)
January 2023
Designed, built, documented, and deployed a cloud-hosted REST API covering student, teacher, parent, attendance, examination, and fee-management modules.
Transaction Aggregation API & Vendor Management Middleware
January 2023
Designed a unified financial transaction service aggregating multiple payment channels with pagination and standardized response contracts.
NIN Verification Service (Identity/KYC)
January 2023
Implemented secure identity validation APIs, linking National Identity Numbers to banking profiles for KYC-style verification flows.
Contact Information
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