Melanie H.

Go backend developer and QA engineer with 13+ years in software engineering, specialising in payments and fintech. GO BACKEND 3 years of Golang development: REST APIs, backend services and integrations, with a strong background in Java (Spring Boot). I care about correctness in money paths - idempotency, retries and testable code. PAYMENTS & FINTECH - Currently a Senior Software Engineer building payment terminal and POS software (Axium terminals, Circle K POS, self-service terminals) for EU markets. - 6+ years on Ingenico/Worldline payment software; refactored payment flows and cut transaction errors by 35%. QA & API TESTING Manual and API testing (Postman, Kreya, OAuth/JWT), test plans and test cases in Jira/Xray, maintaining Python automated tests, and pre-release validation of payment flows. ANDROID Kotlin, Java, Jetpack Compose, MVVM / Clean Architecture, Coroutines, Room, Retrofit, Dagger Hilt, Firebase. Can build or fix the mobile app that talks to your Go backend. 5.0 rating across 13 Upwork jobs. I communicate clearly, deliver on time and take ownership from first build to release. Good fit if you need: a Go API or service, payment/POS integration work, a thorough QA or API testing pass before launch, or Android work.