I'm Žygimantas Sideravičius, a senior software engineer and founder of Siddy Tech, building SaaS platforms, automation systems, and mobile apps across multiple countries. I have 7+ years in production and 10+ systems delivered, including platforms with 10M+ users. I work with startups and growth-stage teams on MVPs, operations automation, legacy rewrites, and replacing cobbled-together tooling with something that actually holds up. My Master's is in DeepTech Entrepreneurship, and that shapes every project I take on. Before anything gets built, I ask: will this actually drive revenue? I push back on the spec when it's pointing in the wrong direction. Async-first, direct, no hand-holding needed. I ship fast, tell you when your idea won’t work, and treat your budget like it’s mine—providing honest feedback and a clear path to value.

Žygimantas Sideravičius

I'm Žygimantas Sideravičius, a senior software engineer and founder of Siddy Tech, building SaaS platforms, automation systems, and mobile apps across multiple countries. I have 7+ years in production and 10+ systems delivered, including platforms with 10M+ users. I work with startups and growth-stage teams on MVPs, operations automation, legacy rewrites, and replacing cobbled-together tooling with something that actually holds up. My Master's is in DeepTech Entrepreneurship, and that shapes every project I take on. Before anything gets built, I ask: will this actually drive revenue? I push back on the spec when it's pointing in the wrong direction. Async-first, direct, no hand-holding needed. I ship fast, tell you when your idea won’t work, and treat your budget like it’s mine—providing honest feedback and a clear path to value.

Available to hire

I’m Žygimantas Sideravičius, a senior software engineer and founder of Siddy Tech, building SaaS platforms, automation systems, and mobile apps across multiple countries. I have 7+ years in production and 10+ systems delivered, including platforms with 10M+ users. I work with startups and growth-stage teams on MVPs, operations automation, legacy rewrites, and replacing cobbled-together tooling with something that actually holds up.

My Master’s is in DeepTech Entrepreneurship, and that shapes every project I take on. Before anything gets built, I ask: will this actually drive revenue? I push back on the spec when it’s pointing in the wrong direction. Async-first, direct, no hand-holding needed. I ship fast, tell you when your idea won’t work, and treat your budget like it’s mine—providing honest feedback and a clear path to value.

See more

Experience Level

Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
See more

Language

English
Fluent

Work Experience

Founder & Lead Engineer at Siddy Tech
January 1, 2024 - Present
Built SaaS platforms and custom web apps for startups and SMBs using React, Next.js, Node.js, and Laravel, covering the full cycle from discovery through architecture, development, QA, and deployment. Built automation workflows (Node.js scripts, scheduled jobs, webhook orchestration) that replaced manual data entry and reporting for multiple clients. Added AI functionality (OpenAI API, Claude API) to client products, including automated customer support and internal document processing. Delivered CRM/CMS platforms built around how clients actually work, replacing generic tools that didn't fit their operations. Managed projects asynchronously across timezones via Slack, Notion, and GitHub, consistently delivering on schedule.
Senior Software Engineer at Syno International
March 1, 2025 - Present
Designing system architecture for performance-critical applications serving 10M+ users. Rewriting legacy codebases into maintainable, performant solutions. Leading engineering decisions across backend services, API layers, and infrastructure.
Senior Software Engineer (Product & Innovation) at NFQ
December 1, 2023 - February 28, 2025
Promoted to Senior Engineer within 12 months for technical leadership and delivery speed. Built and shipped product features for e-commerce platforms in the Shopware ecosystem. Set up message queue systems (RabbitMQ) and containerized deployments (Docker, Kubernetes). Mentored junior engineers on architecture decisions and code quality. Improved CI/CD pipelines, cutting deployment friction and increasing release frequency.
Full Stack Engineer at Seems Neat
November 1, 2019 - November 30, 2023
Core engineer on web and mobile products from the ground up, over 4 years. Built cross-platform mobile apps (React Native, Expo) with real production users, including Bluetooth LE integrations with smart wearables and health devices. Designed and built RESTful and GraphQL APIs (Node.js, Laravel) for multi-client platforms. Worked directly with founders and stakeholders on product direction, priorities, and architecture. Multiple production releases per month, consistently, across web and mobile.
Backend Developer (Raštija.lt) at Vilnius University
April 1, 2019 - April 30, 2021
Built backend systems and APIs for a university digital platform. Early work in API design, database architecture, and PHP development.
Backend Developer at Raštija.lt (Vilnius University)
April 1, 2019 - April 1, 2021
Built backend systems and APIs for university digital platform, focusing on API design, database architecture, and PHP development in early-stage projects.

Education

Master of Business Management at Vilnius University
January 1, 2023 - January 1, 2025
Bachelor's Degree at Vilnius University
January 1, 2018 - January 1, 2022
Master of Business Management at Vilnius University
January 1, 2023 - January 1, 2025
Bachelor's Degree at Vilnius University
January 1, 2018 - January 1, 2022

Qualifications

Add your qualifications or awards here.

Industry Experience

Software & Internet, Professional Services, Education