11/09/2026 updated
100 % available
Senior Software Engineer | Backend, Web & Mobile | ex-Microsoft
Trstenik, Serbia
Only remote
Abitur (Serbien), 1 Jahr Informatikstudium an der TU BrnoAbout me
Senior backend engineer, 10 years. Ex-Microsoft: led Skype auth (100M users, +20% sign-in success), architected the Skype-to-Teams migration, built AI for Teams. Co-founded a B2B platform that processes $1.2M/month in payments. Node.js, TypeScript, AWS, React, Next.js. Remote, CET.
AuthenticationsPostgreSQLMongoDBNode.jsPayment GatewayBlockchainTypeScriptReact.jsExpress.jsElectron (Programming Language)BackendAWS ECSBackend ProgrammingFull Stack DevelopmentApache Kafka
Backend Engineering & Distributed Systems
Expertise in system design, backend performance and scaling, distributed systems, microservices, event-driven systems, API design, and high-throughput transactions. Proven track record of architecting and building multi-service monorepos on AWS covering auth, wallet, ledger, payments, and real-time settlement.
TypeScript, Node.js & JavaScript Frameworks
Deep proficiency in TypeScript and Node.js as primary runtimes, with extensive use of JavaScript frameworks including React, React Native, Vue, and Electron. Also experienced with Kotlin/Java and Swift/Objective-C for cross-platform development.
Cloud Infrastructure & DevOps
Hands-on experience with Azure and AWS cloud platforms, PostgreSQL, Redis, Kafka, Cosmos DB, MongoDB, Docker, and Cloudflare (WAF, rate limiting). Skilled in CI/CD pipelines and observability practices for large-scale production systems.
Identity, Authentication & Security
Ownership of sign-in and identity systems at scale, including authentication lead for Skype with 100M users. Experience with Cloudflare WAF, DDoS protection, AI-assisted fraud detection, user blocking, and audit logging for back-office actions.
Payments & Crypto Integration
Built in-house crypto payment systems supporting 9 blockchain networks (Bitcoin, Ethereum, Solana, Tron, BSC, Base, Polygon, XRP, Litecoin) without third-party processors. Also integrated Cards, Apple Pay, Google Pay, e-wallets, and local payment methods through a licensed payment partner.
Real-Time Communications & Large-Scale Migrations
Led the migration of Skype users to Microsoft Teams on both the Skype and Teams side, enabling Microsoft to shut down Skype in May 2025. Experienced in real-time communications systems and large-scale platform migrations.
AI Features & LLM Integration
Built an AI chat assistant for Teams (SMB) that answers how-to questions and carries out admin and user actions in a Microsoft environment. Domain knowledge in LLMs, AI agents, and AI-assisted fraud detection.
Frontend Architecture & OTT/Streaming Apps
Led front-end development across multiple apps and microservices, including Netflix-style streaming apps for major European broadcasters. Built tooling that generates complex web apps from JSON definitions using TypeScript, React, and D3.js.
B2B Platform Development & Co-Founding
Co-founded BTX Technologies and built a white-label real-money B2B platform from scratch, supporting player sites in 12 languages, back office, CRM, affiliates, and third-party integrations with a shared player balance reaching $1.2M a month in deposits and withdrawals.
Expertise in system design, backend performance and scaling, distributed systems, microservices, event-driven systems, API design, and high-throughput transactions. Proven track record of architecting and building multi-service monorepos on AWS covering auth, wallet, ledger, payments, and real-time settlement.
TypeScript, Node.js & JavaScript Frameworks
Deep proficiency in TypeScript and Node.js as primary runtimes, with extensive use of JavaScript frameworks including React, React Native, Vue, and Electron. Also experienced with Kotlin/Java and Swift/Objective-C for cross-platform development.
Cloud Infrastructure & DevOps
Hands-on experience with Azure and AWS cloud platforms, PostgreSQL, Redis, Kafka, Cosmos DB, MongoDB, Docker, and Cloudflare (WAF, rate limiting). Skilled in CI/CD pipelines and observability practices for large-scale production systems.
Identity, Authentication & Security
Ownership of sign-in and identity systems at scale, including authentication lead for Skype with 100M users. Experience with Cloudflare WAF, DDoS protection, AI-assisted fraud detection, user blocking, and audit logging for back-office actions.
Payments & Crypto Integration
Built in-house crypto payment systems supporting 9 blockchain networks (Bitcoin, Ethereum, Solana, Tron, BSC, Base, Polygon, XRP, Litecoin) without third-party processors. Also integrated Cards, Apple Pay, Google Pay, e-wallets, and local payment methods through a licensed payment partner.
Real-Time Communications & Large-Scale Migrations
Led the migration of Skype users to Microsoft Teams on both the Skype and Teams side, enabling Microsoft to shut down Skype in May 2025. Experienced in real-time communications systems and large-scale platform migrations.
AI Features & LLM Integration
Built an AI chat assistant for Teams (SMB) that answers how-to questions and carries out admin and user actions in a Microsoft environment. Domain knowledge in LLMs, AI agents, and AI-assisted fraud detection.
Frontend Architecture & OTT/Streaming Apps
Led front-end development across multiple apps and microservices, including Netflix-style streaming apps for major European broadcasters. Built tooling that generates complex web apps from JSON definitions using TypeScript, React, and D3.js.
B2B Platform Development & Co-Founding
Co-founded BTX Technologies and built a white-label real-money B2B platform from scratch, supporting player sites in 12 languages, back office, CRM, affiliates, and third-party integrations with a shared player balance reaching $1.2M a month in deposits and withdrawals.
Experience
Professional experience10+ years
Freelancer since2026
Languages
EnglishFluentCzechFluentSerbianNative speaker
Project history
Architected the migration of Skype users to Teams on both the Skype and Teams side, allowing Microsoft to shut down Skype in May 2025. Served as authentication lead for Skype (100M users), owning sign-in and identity and collaborating with other Microsoft product teams on shared auth, engagement, and calling. Increased Skype sign-in success rate by 20% and sign-up success rate by 15%. Built an AI chat assistant for Teams (SMB) that answers how-to questions and carries out admin and user actions in a customer Microsoft environment. Stack: TypeScript, Node.js, React, Electron, Objective-C, Swift, Kotlin/Java. Promoted to Senior Software Engineer in December 2023.
Co-founded BTX and built its white-label real-money platform from scratch, with player sites in 12 languages, back office, CRM, affiliates, and third-party integrations sharing one player balance. Reached $1.2M a month in deposits and withdrawals. Wrote most of the backend as a multi-service monorepo on AWS covering auth, wallet, ledger, payments, real-time settlement, and 10+ in-house games. Built crypto payments in-house on 9 chains with no third-party processor. Owned security and fraud prevention including Cloudflare WAF, DDoS protection, AI-assisted fraud detection, user blocking, and audit logging. Responsible for scaling, incidents, infrastructure, and cost.
Built the front end of Netflix-style streaming apps for YouSee (Denmark's leading TV provider) and NPO (Dutch public broadcasting) from architecture to launch.