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Lead Backend Developer & Architect Distributed · Systems · Event-Driven Platforms

Karel M.

https://www.linkedin.com/in/karel-ma%c5%a1ek-7b80564/
Děčín, Ústí nad Labem, Czechia

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I design and build distributed backend systems that are scalable, maintainable, and operationally resilient — without over-engineering them into abstractions nobody asked for. I believe the best software is simple enough to reason about, tested enough to refactor with confidence, and designed just well enough for what it needs to do today. I've applied this across fintech, digital onboarding, and enterprise platforms: → Event-driven architectures that scale horizontally and handle failure gracefully — with zero downtime in production → Custom DSLs that let non-technical teams configure complex workflows without touching code — compressing enterprise delivery from months to 2–4 weeks → Component models that enable extensibility, reusability, and multi-tenancy — supporting 53+ integrated providers at scale → AI-powered coding agents that cut the time and knowledge barrier to onboarding new integrations Most recently I spent 7 years as Platform Lead at Zenoo — trusted by LSEG, Transunion, Sotheby's, Maples, and Refinitiv — where I designed and built the orchestration engine, analytics ecosystem, and billing infrastructure from the ground up. I work best as a technical lead or individual contributor in small, focused teams — the kind of role where I own architecture end-to-end and ship systems that last. Building something that needs to scale and not break? Send me a message here on LinkedIn.

Skills

Java 20

Experience

Platform Lead Developer

Zenoo 7 yrs 5 mos

Zenoo is a digital onboarding platform trusted by LSEG, Transunion, Sotheby's, Maples and Refinitiv. I joined as the platform developer and built the core engine from zero.

▸ Execution Engine & Platform

Designed and built Hub — the orchestration and workflow execution engine at Zenoo's core — from the ground up using Java 21, Spring Boot 3, Project Reactor, and an event-driven backbone built on Apache Kafka and Kafka Streams. Engineered for horizontal scalability and fault tolerance, delivering zero downtime in production

Built a custom DSL that let product and delivery teams define complex KYC/AML workflows declaratively, compressing enterprise onboarding delivery from months of custom development to 2–4 weeks

▸ Plugin System & Component Model

Designed a plugin architecture and component model that turned each vendor integration into a reusable, independently configurable unit — supporting 53+ integrated identity, screening, and monitoring providers

The component model enabled multi-tenancy at enterprise scale — giving each client full configurability and testability

▸ Analytics & Billing

Built the analytics ecosystem and automated billing infrastructure from scratch — gave the business real-time visibility into per-client workflow usage and replaced manual revenue tracking with automated monetization.

▸ AI Coding Agent

Built an AI-powered developer agent that automated the generation of API integration code for Hub plugins — reduced the domain knowledge barrier and cut the time to onboard a new third-party provider into the platform

Stack: Java 21 · Groovy · Spring Boot 3 · Project Reactor · Apache Kafka · Kafka Streams · Redis · AWS (DynamoDB, MSK, Secrets Manager) · Docker

Lead Developer, Architect, Business Analyst

4finance 5 yrs 3 mos

▸ US Lead Handler

Designed and delivered a microservice loan processing system with a custom underwriting DSL — let risk and product teams adjust loan filtering logic without engineering involvement.

▸ 4Spar

Developed and maintained applications for managing deposit accounts. Led the migration from a legacy monolith to a modern microservice architecture (DDD, CQRS). Took on BA responsibilities alongside technical lead. Owned requirements, architecture, and delivery simultaneously across both projects.

Stack: Java 8 · Groovy · Spring Boot / Cloud / Data · REST · Hibernate · Camel · Zookeeper · Hystrix · Grafana · Angular.js

Senior Java Developer, Freelance consultant

Monster Government Solutions 3 yrs

Senior contributor on a federal HR platform spanning 15+ production applications — took ownership of cross-cutting refactors that improved stability and reduced the defect surface across all dependent systems. Profiled and resolved performance bottlenecks on critical request paths — delivered measurable latency improvements. Designed and delivered multiple comprehensive features from DB schema through production.

Stack: Java · Spring MVC / Security · Hibernate · Oracle 11g · Groovy · Drools · PL/SQL · REST · TDD (TestNG, Mockito)

SOFA2 and OSGi integration

Distributed Systems Research Group, MFF UK 1 yr

Demonstrated interoperability between SOFA2 component system and OSGi Service Platform — validated in a peer-reviewed IEEE publication at EUROMICRO SEAA 2009.

Publication: Masek, K., Hnetynka, P., Bures, T.: Bridging the component-based and service-oriented worlds, In proceedings of EUROMICRO SEAA 2009, Patras, Greece, IEEE CS, ISBN 978-0-7695-3784-9, pp. 47-54 http://d3s.mff.cuni.cz/publications/masek-hnetynka-bures-bridging.pdf

Stack: Java · OSGi · Apache Felix · Eclipse Modeling Framework · ASM

Integration Software Engineer, Permanent employee

Sun Microsystems, Czech Republic 4 yrs

Designed and built the integration layer, custom workflows, and platform customizations for Sun's migration from an internal translation management system to Idiom WorldServer — worked directly with existing teams to migrate their projects and processes to the new platform. Built and maintained two production web applications for managing translation projects — owned feature design, delivery, testing, and user support end-to-end across a 4-year tenure.

Stack: Java · JEE · EJB 2.1 · JMS · Oracle 10g · Web Services · XML/XSLT · Struts · SQL/PL/SQL · Solaris 10

Software Engineer, intern

Sun Microsystems, Czech Republic 1 yr

Converted to permanent employee within 12 months — recognized for delivery quality on the translation management platform. Continued owning feature design, implementation, and user support after conversion.

Stack: Java · JEE · Oracle 10g · Web Services · Struts · JSP

Distributed sniffer Čuvač

Network and Labs Management Center, MFF UK 2 yrs

• developing a distributed sniffer with GUI interface to monitor, capture and analyze network traffic • C, C++, Gtk, TCP/IP, libpcap, multi-threading, Linux