Looking for a job

Boris Kardelis

@boriskardelis

Message

I build reliable Kotlin payment, billing, and high-volume transaction systems.

Serbia

Message

What I'm looking for

I'm looking to own architecture and delivery for correctness-critical backend systems, especially payments, billing, reconciliation, and distributed transaction platforms, while mentoring engineers and improving engineering standards.

At Ximedes, I build TapConnect’s multi-tenant ticketing platform for European public transport operators, including the Deutschlandticket rollout. I’ve owned subscription, ticketing, PAYG billing, and reconciliation flows, issuing more than 100,000 tickets without degradation during a major Rotterdam rollout.

I bring eight years across fintech and mobility, including Rabobank’s PSP platform, where I built recurring payment and invoicing pipelines, improved reconciliation storage for millions of transactions, and helped migrate services from on-premise Java to the cloud. I work primarily in Kotlin/JVM, AWS, PostgreSQL, and distributed systems, while mentoring engineers and raising architecture and code review standards.

Experience

Work history, roles, and key accomplishments

Current

Senior Backend Engineer

Current

Ximedes

Sep 2021 - Present (5 years)

Senior Backend Engineer on TapConnect, a multi-tenant ticketing platform for European public transport operators. Led backend integration for the Deutschlandticket rollout and owned subscription and ticketing flows, including barcode and mobile ticketing, PAYG billing, and enrollment.