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Mykyta Belimenko

@mykytabelimenko

Senior Java backend engineer at T-Mobile who made a catalogue API 50× faster and built billing services processing 100,000+ monthly transactions.

Czechia

Message

At T-Mobile, I led architecture for a catalogue of 100,000+ products serving Czechia, Slovakia, Germany, and Austria. I cut a key aggregated-catalogue API response from 35 minutes to 40 seconds by profiling queries and indexing PostgreSQL materialized-view access paths.

I shipped about 100 biweekly production releases with rollback plans, automated tests, feature flags, and Helm rollouts. I also evolved REST APIs, introduced gateway authentication, and designed Kafka integrations for large catalogue transfers.

Before that, I built Java and Spring Boot billing services at T-Mobile that processed 100,000+ monthly transactions for App Store, Google Play, and third-party subscriptions. At DHL, I led architecture and delivery for a global API catalogue and developer portal used daily by hundreds of engineers.

Experience

Work history, roles, and key accomplishments

Senior Software Engineer / Lead Architect

T-Mobile

Sep 2022 - Sep 2026 (4 years)

Led architecture of a 100,000+ product catalogue serving four countries, cutting a key API response from 35 minutes to 40 seconds. Shipped ~100 biweekly releases and mentored 8 engineers.

Java 21+Spring Boot Kafka PostgreSQL Kubernetes GitLab CI CD REST API Versioning Liquibase Microsoft Entra ID OIDC Spring Security Avro Playwright Helm Feature Flags

Senior Software Engineer / Technical Lead

DHL

Apr 2021 - Aug 2022 (1 year 4 months)

Led DHL's global internal API catalogue and developer portal, bringing thousands of APIs into one searchable portal. Owned architecture and delivery using Vue.js and Node.js/NestJS.

Vue.Js NodeJS NestJS API Management DevPortal Architecture Cross team coordination

Senior Software Engineer

T-Mobile

Dec 2017 - Apr 2021 (3 years 4 months)

Built Java/Spring Boot microservices processing 100,000+ transactions a month for carrier billing. Implemented charging flow and promoted to Senior Software Engineer.

Java Spring Boot Microservices REST PostgreSQL SMS Notifications Callbacks Technical Interviews Mentorship

Software Engineer

Koukatko

Feb 2016 - Dec 2017 (1 year 10 months)

Built Java/Spring Boot and Spring Cloud microservices with REST, GraphQL, RabbitMQ, PostgreSQL, and Elasticsearch, and a Vue.js product-catalogue frontend.