09/14/2026 updated
AJ
100 % available
Senior Backend Engineer | Product Systems & Financial Workflows
Београд, Serbia
Only remote
B.Sc. Mathematics - Faculty of Sciences, University of Novi SadAbout me
I aim to be responsible, versatile and effective
Application Programming Interfaces (APIs)PostgreSQLNode.jsTypeScriptBackendGraphQLFront End Software DevelopmentApi Design
Backend Development & API Design
Expertise in building backend services and APIs using TypeScript, JavaScript, Node.js, REST and GraphQL. Design and implementation of service integrations and asynchronous workflows across complex, customer-facing products.
Data Engineering & Reliability
Proficiency in PostgreSQL, SQL and Prisma for relational data modeling, validation and failure recovery. Strong focus on production debugging and building reliable, maintainable data layers.
Cloud Infrastructure & Delivery
Hands-on experience with AWS, Docker, Linux and CI/CD pipelines. Delivery of scalable systems using Git, React and Next.js, with additional knowledge in Python and C/C++.
Product Engineering & Architecture
Translation of ambiguous requirements into technical implementation plans. Cross-functional delivery, operational workflow design, architecture decisions, code review and mentoring of engineers.
TypeScript & Open-Source Tooling
Creation of open-source frameworks and reusable TypeScript tools, including a contract-first API framework (APISPECTS) and utilities for fuzzy search, interval operations, command registries and tree/graph data structures.
E-Commerce & Real-Time Systems
Building and maintaining systems supporting e-commerce, content management and real-time data-processing workflows, including a complete ordering system built around the constraints of a live food-retail operation.
Financial Software & High-Frequency Trading
Experience building transaction-oriented financial software and leading frontend development for a high-frequency-trading product, translating a fast-moving financial domain into maintainable application behavior.
Technical Leadership & Mentoring
Teaching programming, mentoring engineers in TypeScript, React, API design and system architecture, and delivering company-wide technical sessions to audiences of approximately 50 engineers.
Distributed Systems & Media
Building distributed services for agent execution, real-time media and private-network communication across Linux, mobile and wearable devices.
Expertise in building backend services and APIs using TypeScript, JavaScript, Node.js, REST and GraphQL. Design and implementation of service integrations and asynchronous workflows across complex, customer-facing products.
Data Engineering & Reliability
Proficiency in PostgreSQL, SQL and Prisma for relational data modeling, validation and failure recovery. Strong focus on production debugging and building reliable, maintainable data layers.
Cloud Infrastructure & Delivery
Hands-on experience with AWS, Docker, Linux and CI/CD pipelines. Delivery of scalable systems using Git, React and Next.js, with additional knowledge in Python and C/C++.
Product Engineering & Architecture
Translation of ambiguous requirements into technical implementation plans. Cross-functional delivery, operational workflow design, architecture decisions, code review and mentoring of engineers.
TypeScript & Open-Source Tooling
Creation of open-source frameworks and reusable TypeScript tools, including a contract-first API framework (APISPECTS) and utilities for fuzzy search, interval operations, command registries and tree/graph data structures.
E-Commerce & Real-Time Systems
Building and maintaining systems supporting e-commerce, content management and real-time data-processing workflows, including a complete ordering system built around the constraints of a live food-retail operation.
Financial Software & High-Frequency Trading
Experience building transaction-oriented financial software and leading frontend development for a high-frequency-trading product, translating a fast-moving financial domain into maintainable application behavior.
Technical Leadership & Mentoring
Teaching programming, mentoring engineers in TypeScript, React, API design and system architecture, and delivering company-wide technical sessions to audiences of approximately 50 engineers.
Distributed Systems & Media
Building distributed services for agent execution, real-time media and private-network communication across Linux, mobile and wearable devices.
Experience
Professional experience5 - 10 years
Freelancer since2026
Languages
EnglishFluent
Project history
Created an open-source framework where one validated specification generates typed server routes, client SDKs and a uniform error model, keeping contracts synchronized across service boundaries. Designed the public API, schema model, runtime behavior, generated types, documentation and examples. Focused the design on durable integration boundaries: shared validation, compile-time guarantees and consistent propagation of failures between server and client. Built with TypeScript, Node.js and Zod.
Built and operated a complete ordering system around the constraints of a live food-retail operation. Designed the relational model for customers, phone numbers, carts, orders and trust state; implemented APIs, customer flows, a worker interface, deployment and production recovery paths. Modeled ambiguous carts, interrupted calls, unavailable workers and manual recovery as explicit system states. Built with TypeScript, Next.js, Node.js, Prisma, SQL and SIP/telephony.
Owned technical delivery across customer-facing products, backend services and integrations using TypeScript, Node.js, React and AWS. Built and maintained systems supporting e-commerce, content management and real-time data-processing workflows. Translated product needs into implementation direction and coordinated changes across service, team and stakeholder boundaries. Remained hands-on with architecture, critical implementation, code review, releases and production issues while guiding and mentoring engineers. Promoted to Lead Software Engineer in 2025.