Profile/ identity.readme

01IDENTITY / README

ENGINEERSoftware Engineer

Szymon
Leja

Business-critical software across Java, Spring, React, and distributed systems.

I build and optimize enterprise applications for global financial and technology teams, from microservices to frontend platforms and cloud delivery.

WORKING SET

JavaSpring BootReactPostgreSQLDocker

INTERESTS

Systems designAI automationGame developmentGraphics & low-level systems

Experience/ career.log

02CAREER.LOG / EXPERIENCE

Production
history.

01

EPAM Systems2 ENGAGEMENTS

Leading Global Investment Bank

Senior Software Engineer

Apr 2026 — Present

Contributed to migrating a complex mobile frontend from multiple repositories into a pnpm monorepo, consolidating 15 CI/CD pipelines into one. Resolved React and Redux state issues, integrated with Java and Spring services, and remediated security vulnerabilities.

JavaSpring BootReactReduxTypeScriptpnpmAzure

Global Technology Leader

Senior Software Engineer

Jun 2025 — Apr 2026

Developed Java and gRPC backend services and Angular and TypeScript interfaces for a large-scale enterprise platform, using internal dependency-injection frameworks and asynchronous processing. Worked closely with UX and engineering teams through Figma and in-depth code reviews.

JavagRPCRBACGuiceAngularTypeScriptGCP

02

T-Mobile PolskaEMPLOYER

Full Stack Developer

Jun 2023 — May 2025

Built customer-support tooling for analyzing issues and checking real-time service status. Delivered React and TypeScript interfaces and Java and Spring Boot microservices, integrated Oracle and PostgreSQL, and owned features from requirements through CI/CD and Kubernetes deployment.

JavaSpring BootReactReduxPostgreSQLRedisKubernetes

03

Idego GroupEMPLOYER

Senior Software Engineer

Jun 2024 — Dec 2024

Architected a monolith-to-microservices migration using Hexagonal Architecture and modernized legacy micro-frontends for Azure deployment.

JavaSpring BootReactDockerAzurePostgreSQL

04

NokiaEMPLOYER

Java Software Engineer

Oct 2021 — May 2023

Maintained and developed software-management tooling for network masts across Java, Spring Boot, and Go. Built a Java reflection library that generated documentation and UML diagrams directly from the codebase.

JavaSpring BootGoJava ReflectionUMLREST APIs

05

Sky Blue EducationEMPLOYER

Software Engineer

Jul 2020 — Nov 2022

Designed and built tailor-made CRM and CMS systems from scratch, then maintained the applications, databases, and public websites.

PHPJavaScriptMySQLWordPress

Skills/ capabilities.index

03CAPABILITIES / INDEX

Working
set.

01

Languages

JavaTypeScriptGoPythonSQL

02

Backend & Architecture

Spring BootRESTgRPCRabbitMQKafkaGuice

03

Frontend

ReactReduxAngularNext.jsReact Native

04

Data

PostgreSQLOracleRedisMongoDBQdrant

05

Cloud & Delivery

DockerKubernetesCI/CDGCPAzureAWSTerraform

06

Quality & AI

JUnitCypressPlaywrightGrafanaPrometheusRAGLLMs

Contact/ channel.open

04I/O / CONTACT

Open a
channel.

For engineering work or a technical conversation, choose a route below.

leja.dev linkedin.com/in/szymon-leja

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Szymon LejaSenior Software Engineer

Szymon Leja

Production history.

EPAM Systems2 ENGAGEMENTS

Senior Software Engineer

Senior Software Engineer

T-Mobile PolskaEMPLOYER

Full Stack Developer

Idego GroupEMPLOYER

Senior Software Engineer

NokiaEMPLOYER

Java Software Engineer

Sky Blue EducationEMPLOYER

Software Engineer

Workingset.

Languages

Backend & Architecture

Frontend

Data

Cloud & Delivery

Quality & AI

Szymon
Leja

Production
history.

Working
set.