JZJiří ZrníkPrincipal developer for ambitious digital products Česky / .cz

Web / Mobile / Desktop

Full-stack development with product depth and enterprise discipline.

I design and ship modern software for founders, product teams and enterprise clients. My focus is fast, maintainable delivery across Angular frontends, robust backend platforms, mobile apps and specialized desktop systems.

Based in the Czech RepublicAvailable for consulting, delivery and modernization work

Why clients hire me

Built for teams that need senior execution, not supervision.

Product thinking

I do not stop at code. I help shape technical direction, reduce delivery risk and keep features aligned with business outcomes.

Wide technical range

From Angular and APIs to native mobile, desktop tooling and trading systems, I can bridge product layers without creating handoff friction.

Battle-tested delivery

My background includes venture-backed products, enterprise platforms and specialized internal systems where reliability matters as much as speed.

Services

A focused senior partner for new builds, difficult rewrites and high-value product work.

The current site is intentionally concise. The goal is to make the value proposition clearer than the original portfolio while still grounding it in real delivery experience.

Product engineering

New apps, new modules or greenfield systems built with a pragmatic architecture that supports growth.

  • Angular frontends and design implementation
  • Backend APIs and integrations
  • Performance, accessibility and maintainability

Modernization and rescue

Legacy systems, unstable releases or unclear architecture turned into software that teams can safely evolve.

  • Incremental rewrites
  • Technical debt reduction
  • Codebase stabilization and delivery cleanup

Specialized systems

Solutions beyond standard websites, including mobile, desktop, hardware-linked apps and data-heavy products.

  • Desktop and device integrations
  • Real-time features and WebRTC
  • Automated trading and analytical tooling

Selected work

Products delivered across real commercial domains.

A broader sample of products delivered across consumer apps, enterprise systems and revenue-generating platforms, framed to make stack fit and delivery depth clearer.

Outdoor mobile product

Hill Explorer

Native Android app for mountain orientation and place discovery, backed by C# services and SQL, with offline usage, GDAL and DEM-based terrain work, rich point-of-interest data and shareable visual output.

AndroidNative JavaC#SQLGDAL / DEM

Mobile game product

Puzzolver

Logic puzzle game for mobile devices delivered as a complete product, from gameplay implementation and level design support to release-ready polish and app-store presence.

AndroidNative JavaMobile UXGame Logic

Sports platform

Fanwide

Principal development work on a product connecting sports fans nationwide, covering product delivery and platform engineering.

ASP.NET MVCWeb APIMongoDBAngular

Algorithmic trading

ZoBot

A continuously improved automated trading system combining machine learning, analytics and performance-focused engineering.

MQL5C#C++AI / ML

Enterprise tooling

Instrument editor platform

A universal web-based editor built for enterprise usage with broad applicability and a maintainable Angular architecture.

AngularTypeScriptSass

Scheduling and operations

Event scheduler platform

Planning software for events, teams and venues with calendar-heavy workflows, conflict handling, automated notifications and operational reporting for staff and managers.

Angular.NETSQLScheduling

Commerce platforms

Custom e-commerce systems

Online stores and B2B sales portals with product catalogs, pricing logic, order flows, payment integrations and administrative tooling tailored to the business model.

AngularC#SQLPayments

Media delivery

Video streaming applications

Streaming-oriented applications combining media catalogs, secure playback flows, subscription logic, back-office management and analytics for content and usage.

Angular.NETStreamingAnalytics

Access and attendance systems

RDX and GT800 ecosystem

Services and applications for readers, smart cards, fingerprint devices, attendance monitoring and Windows integrations.

C#C++COMNative Java

Automation software

Workflow and integration automation

Internal software for repetitive business processes, data synchronization, device communication and background operations that reduce manual work and operational error rates.

C#APIsSQLAutomation

AI-enabled product features

Applied AI and assistant workflows

Modern product features around AI-assisted search, classification, recommendations and workflow copilots, integrated pragmatically into existing applications instead of treated as standalone demos.

AILLM IntegrationsC#TypeScript

How I work

Clear collaboration, fast iteration, direct ownership.

01

Audit the real constraints

I start by identifying the genuine bottlenecks: architecture, delivery process, product ambiguity or legacy complexity.

02

Design the smallest effective move

Instead of overengineering, I aim for the narrowest solution that creates momentum and keeps future options open.

03

Ship and harden

The goal is not a demo. The goal is production-ready software with sensible quality, observability and room to grow.

Contact

Need a senior developer who can own the hard parts?

If you are building a new product, modernizing an existing platform or need help with a demanding technical problem, send me a short brief and I will respond directly.