I'm René Klačan and I love building software.

I am a husband, father of two, and a T-shaped software engineer with experience in designing and working on large-scale systems.

I'm co-founder of FirstLook.gg, a platform that helps game studios manage their playtesting.

Previously I was CTO at FetLife, a kinky social network which is with more than 1M daily active users, one of the largest Rails applications in the world.

I am also creator of AoE4 World, the largest community website for Age of Empires 4 game.

During my spare time, I love to be active, currently mainly lifting weights and running. But I also enjoy cycling, hiking, climbing, and yoga.

While I have plenty of experience with frontend and infrastructure, my biggest passion is backend development, systems architecture, and performance optimization throughout the whole stack. In other words, I love building scalable, performant, reliable, and cost-effective systems.

My language of choice is Rust but I'm comfortable working with pretty much any language and I believe in always using the right tool for the job.

I have experience managing small teams but it is something I don't enjoy nor am I exceptionally good at, so I only want to focus on what I love the most - building great software.

Experience

Co-Founder at FirstLook.gg

Feb 2024 - Present

FirstLook.gg is a platform that simplifies onboarding and managing game playtesters. It automates tasks like inviting players, redeeming Steam keys, managing NDAs, and providing Discord access. With a customizable onboarding experience, it allows studios to connect with testers seamlessly, making it ideal for multiplayer or large-scale beta tests and freeing developers to focus on game improvement.

Backstory: Our journey began when we worked with Frost Giant Studios to help them onboard thousands of playtesters. After the success of the project, a couple of other studios reached out and expressed their interest in similar solution so we decided to turn it into a product.

Team: 2 co-founders

Tech Stack: Typescript (Astro, Solid), Rust, PostgreSQL, Redis, Tailwind CSS

Feb 2024 - Present

CTO at FetLife

Sep 2015 - Nov 2024

FetLife is a kinky social network for the BDSM, Fetish & Kinky community. Fetlife's mission is to help people feel comfortable with who they are sexually.

Key points:

Joined as Senior Engineer, became Engineering Team Lead in Apr 2016 and later got promoted to CTO in Aug 2016.
Managed small remote team.
Continuously collaborated with CEO on making sure technical vision is aligned with company vision.
Responsible for infrastructure & application architecture and hands-on development of the entire platform.
Actively participated in hiring.
Since I joined the traffic grew more than 20x and we managed to keep average response time under 200ms.
Led migration from bare-metal servers to Google Cloud Platform.
Performance optimization throughout the whole stack.
Designed and implemented iterations of user recommendations service using Python and later Rust.
Designed, implemented, and evolved activity feed backend (initially build in Ruby on top of Redis, later in Rust on top of ScyllaDB).

Team: 10-20 employees

Scale: 1M+ daily active users & 3B+ requests per day

Tech Stack: Ruby, Javascript/Typescript (Vue), Rust, Go, GCP, Kubernetes, MySQL, PostgreSQL, Redis, Elasticsearch, ScyllaDB, BigQuery, Terraform

Sep 2015 - Nov 2024

Founder of AoE4 World

Dec 2021 - Present

AoE4 World is a community website for Age of Empires 4 game. Since its launch, it has become the most popular Age of Empires 4 community website for players and it's also the backbone of most community developed tools through its API.

Backstory: What I love even more than playing games is programming so after playing AoE4 for a while after the release I noticed the lack of any site analyzing the game data like civ win/pick rates so I decided to build one. After building a prototype over the weekend, I released it on Reddit and it immediately got some love from community which motivated me to keep working on it.

Key points:

Founded a project which started as simple statistics website.
We grew site to become the main hub for all AoE4 players.
Because of lack of public APIs I reverse-engineered game's internal API calls.
Reverse-engineered game's internal game summary format and wrote a parser to extract interesting game info including build orders (not even available in the game).
Implemented a REST API to serve other community developers (used by the most popular Twitch overlay).
Worked with tournament organizers to provide exclusive statistics.
Deployed and managed infrastructure on GCP.

Team: 2 core developers & 1 active contributor

Scale: 115k users per month & 40M requests per month

Tech Stack: Ruby, Typescript (Vue, Solid), C#, Python, GCP, Kubernetes, PostgreSQL, Redis, Terraform, Tailwind CSS

Dec 2021 - Present

Founder of Korektor

Aug 2017 - Present

Korektor is a grammar corrector for Slovak language and with its userbase it's currently the most popular service of its kind in Slovakia.

Backstory: I started working on this project to help my wife who is a dyslexic, as I saw her struggling on daily basis I wanted to help her.

Key points:

Designed and implemented a statistical and rule based corrector for Slovak language in Rust.
Built document editor with spellcheck and grammar check functionality using React.
Built a Chrome extension and Google Docs plugin.
Deployed and managed infrastructure on GCP.

Team: Just me

Scale: 30k users per month

Tech Stack: Ruby, Rust, Javascript (React), GCP, Kubernetes, PostgreSQL, Redis

Aug 2017 - Present