Vanja Serdar

Senior .NET Software Engineer with 20+ years building enterprise and cloud-based distributed systems across fintech, payments, healthtech, and financial services. Most recently led a team of three engineers (two senior, one junior) at a US fintech scale-up, staying hands-on across architecture, integrations, and delivery. Particular depth in authentication/identity systems, payment and compliance integrations, and .NET/Azure platforms, with recent experience embedding AI-assisted development workflows (Claude) into the day-to-day SDLC.

Team Lead – Software Engineer at Biller Genie (2025-07 – 2026-08)

Biller Genie is a US-based accounts receivable automation company, integrating with accounting software such as QuickBooks and Xero to help businesses send invoices, follow up on payments, and reconcile transactions.

• Led a team of three software engineers (two senior, one junior): partnered with development managers and the architect on project planning, technical guidance, and release/branch synchronization across teams
• Integrated Biller Genie's platform with Mastercard RPPS (electronic bill payment), Sardine's KYC/KYB APIs (identity verification, fraud and risk scoring), and the Elavon EPG payment gateway (card payments for invoices)
• Embedded Anthropic Claude models into the team's development workflow, applying a standardized, team-built Claude Skills process to take tickets from requirements to production-ready code
• General development and maintenance across the platform

Senior Software Engineer at ESO (2023-03 – 2025-05)

ESO provides software for EMS agencies, fire departments, and hospitals to collect, share, and analyze critical information for community health and safety.

• Built authentication features for the ESO Login Portal and Identity API: 2-step login (password/SSO), TOTP registration and authentication with QR codes, and an encryption service using Azure Key Vault
• Developed SAML-based SSO integration across ESO's web applications, including the configuration API and the admin UI used to set up and test SSO before activating it for a client
• Migrated the ESO Identity API from EF6 to EF7 (including the related move from in-process to isolated-worker Function Apps) and led migration of the ESO Login Portal from Angular 12 to Angular 15, including a full visual redevelopment
• Built MFA/SSO administration and client/session search tooling for ESO's internal Admin and Toolbox applications
• Release coordinator on team rota

Software Engineer at eShopWorld (ESW) (2020-08 – 2022-10)

ESW provides e-commerce infrastructure — compliance, fraud protection, taxes, checkout, and delivery — for major retailers and brands.

• Maintained and developed features across ESW's Monolith API/eCron ecosystem; wrote SQL Server stored procedures and managed periodic database comparison and release into production
• Contributed to the initial build of the Document Template Engine API and the Promotion Campaign Management API for a major retailer
• Designed and published Email Template Generator (ETG) HTML templates and translations to production SendGrid accounts

Senior Software Engineer at Viridian Group (2019-01 – 2020-03)

Viridian Group (now Energia Group) is an energy utility company.

• Rewrote the Price Forecasting/Pricing systems and the MRSO customer registration data processing application
• Converted 9 legacy console applications into.NET Core 3.1 Windows Services
• Rebranded the Power NI customer website and extended the Unmetered Data and customer letter applications

Senior Software Engineer at Citi Bank (2017-04 – 2019-01)

• Improved performance and UI responsiveness of an in-house proprietary trading system via an asynchronous execution module and parallelized processing
• Prototyped a 64-bit process to extend data capacity for the existing 32-bit trading application

Senior Software Engineer at DARD (now DAERA), NI Government (2014-08 – 2017-04)

• Built WCF/Web API services and multithreaded Windows Services (Azure message bus monitoring/messaging) for Common Agricultural Policy, Land Entitlements, and Environmental Farming Scheme systems
• Developed SQL Server database logic and MVC/Angular 1.5 UI components; generated XML for the DROOLS rule engine

Software Developer at ANDOR Technology (2012-09 – 2014-04)

• WPF/MVVM UI modules and a low-level acquisition device interface for microscopy imaging systems

Software Developer at SITA (2011-10 – 2012-05)

• Development and knowledge transfer following a company acquisition

Software Developer at Commerzbank AG (2011-01 – 2011-09)

• Rewrote a critical nightly SQL Server stored procedure for the Pandora risk management application after it began overrunning its processing window, cutting runtime from ~18–20 hours to around 1.5 hours and eliminating the resulting job backlog

Software Developer at CDO Software Ltd (2008-09 – 2010-08)

• Built a grid-computing solution with multithreaded nodes for structured credit risk calculation

Software Developer at GMAC RFC (2007-02 – 2008-06)

• Full lifecycle development, maintenance and support for internal systems at a top-10 UK subprime mortgage lender