About me
I have 12 years of experience across the full spectrum -- from embedded systems and chip calibration (C++/C#) to distributed backend platforms (Kotlin/Java/Spring Boot). I've worked in computer vision hardware, enterprise contact centers, fintech payments, and B2B lending.
At Billie, I own the Compliance Service covering transaction monitoring and screening, sit on the architecture team, and drive initiatives like API-first design across services, CI pipeline improvements, and AI adoption. Before that, I spent 4.5 years at SumUp building platform libraries, migrating legacy data, and establishing service templates.
I write about Kotlin and backend engineering at kotlinbackend.com, contribute to open source projects like openapi-generator, and maintain ff4k -- a Kotlin Multiplatform feature flags library.
Education
Experience
Staff Software Engineer - Payments
Established the Compliance Service as a new domain covering transaction monitoring, screening, and sanction checks – authored the tech spec, interface definitions, and led the ComplyAdvantage integration. Built a cronjob monitoring tool in Backstage aggregating data across multiple systems. Authored operational runbooks for Kafka DLT alerts, settlement reports, and compliance state handling. Member of the architecture team. Drove Spring Boot 3 to 4 migration including upstream contributions to openapi-generator for Jackson 3 support.
Staff Software Engineer - Risk
Co-designed and built the Risk Orchestrator service using hexagonal architecture. Led the Ravelin integration for improved fraud detection, including release planning and cross-team coordination. Authored the Buyer Risk Assessment target architecture. Wrote specs for tokenization, direct debit risk, and recurrent identification. Drove API-first with OpenAPI across all risk services. Led “EDA 2.0” to improve event-driven architecture practices.
Senior Software Engineer - Risk
Built real-time fraud detection features with Apache Flink (velocity features per email/device). Led the graph database POC (Neo4j) for fraud detection, later extended with IBAN integration. Enabled the risk scoring model and introduced provider fraud labelling for refinancing. Applied engineering best practices to Python CI/CD pipelines. Managed Kafka infrastructure via Terraform (topic creation, permissions, DLT retention). Attended Flink Forward 2024 and brought learnings back to the team.
Backend Software Developer
Built a unified money library used across backend and Android. Created an authorization and permissions management library. Designed a sales management platform with clean domain separation. Migrated 6 years of historical data with minimal production impact using a separate deployment strategy. Reduced new service setup from 1 week to 1-2 hours with a repository template. Implemented service-level objective monitoring. On-call for critical payment systems.
Backend Software Developer
Java and Python application development on distributed systems. Refactored a product’s cache system improving performance and reliability. Built an automated release notes generator integrating Python 3 and Jira.
C++/C# Junior Developer
Developed algorithms on next-generation vision processing chips in C++. Created calibration processes for production lines (C++, C#, Python, Matlab). Established production lines in South Korea and China – logistics, equipment setup, and training.
Projects & Contributions
ff4j (contributor)
Authored the javax-to-jakarta namespace migration. Merged but never released by maintainers – the motivation for building ff4k.
TaleKeeper
AI-powered TTRPG session recorder with live transcription, speaker diarization, and session summaries. Python/FastAPI backend + Svelte 5 frontend. Fully self-hosted.
ff4k
Kotlin Multiplatform feature flags library with DSL configuration, multiple storage backends (JDBC, R2DBC, SQLite), and coroutine-safe context propagation. Built from scratch as a modern alternative to ff4j.
Konsist (contributor)
CI pipeline improvements, snippet verification, and null handling fixes for the Kotlin static code analyzer. 3 merged PRs.
openapi-generator (contributor)
Added Spring Boot 4 and Jackson 3 support for the Kotlin Spring generator. 10 PRs including fixes for Retrofit templates, Jackson converters, and hashmap model generation.
exekutor
Plugin architecture demo in Kotlin. Demonstrates extensible application design patterns.
kotlin-design-patterns
Software design patterns implemented in idiomatic Kotlin. Actively maintained with MkDocs documentation site.
Beat The Machine
AI-powered guessing game where players identify prompts used to generate images. Built as a university project, later rewritten with DDD.
Emma's Inferno
Atmospheric puzzle-platformer exploring themes of morality. University capstone project.
What others say
Yonatan is a highly talented and disciplined software developer, with an excellent background in both computer science and programming. He is a people-person, with remarkable empathy and ability to recognize when and where students and developers need help and further guidelines. He is also a very pleasant and good-spirited colleague.
I was privileged to have Yonatan on my team for almost 3 years. Yonatan is a dedicated, intelligent, and hard-working team player who played a key role in our team and was the go-to person for almost any problem. I have seen few people who could match his skills at solving technical problems, coding and design.
I’d love to work with Yonatan again. He’s incredibly smart, cares deeply about quality but balances this with delivery speed, and (maybe most importantly) a great human to be teammates with.
