Experience and references

I’m Marek Lecián, a Principal Web Analyst. I have worked in web analytics since 2012, connecting measurement strategy, technical implementation and data analysis with AI, SEO and development.

This page brings together projects I have worked on, recommendations from people I have worked with, and examples of my professional work. It also explains the skills and tools I use in practice.

Selected projects and recommendations

Recommendations originally written in English retain their original wording. Translations from Czech are labelled below, and longer recommendations are excerpted. All quotations are used with the authors’ permission. Project dates and roles refer to the period of collaboration; recommendation dates are listed separately where known.

Alma Career Slovakia: analytics and shared expertise

Working with Roman Hamrák since 2023.

Roman and I work on web analytics for Alma Career’s Slovak team. Our collaboration covers implementation details, data analysis and exploring practical uses of AI. I value our technical discussions and the experience we share with each other.

Marek was one of the main reasons I decided to join Alma Career Slovakia (formerly Profesia.sk) over three years ago. He is a true web analytics legend in the industry. Working alongside him ever since has been an incredible ride, and I’ve grown immensely both professionally and personally.

What I admire most about Marek is his relentless drive and kind personality. He never rests on his laurels, always out there, exploring. His knowledge in the field of AI, deep technical curiosity, and absolute professionalism put him at the very top of his field. At the same time, he manages to keep a healthy emphasis on work-life balance, mental health, and preventing burnout, which is super inspiring and has a positive impact.

[…] Marek is the rare kind of person everyone would be lucky to have as both a colleague and a friend. I couldn’t recommend working with him more.

Roman Hamrák, Digital data analyst, Alma Career Slovakia · Recommendation dated 24 August 2026 · Roman’s professional profile

investigace.cz: analytics for independent journalism

Working together since 2023.

I help the editorial team set up web analytics and report on website traffic. I also advise on finding and verifying information. I support the project pro bono.

Translated from Czech:

Marek has been helping the investigace.cz editorial team with website analytics for several years without charging a fee. He does outstanding work for us. Working with Marek has helped us understand that truly understanding our website visitors takes much more than reading Google Analytics. Marek is an analyst and programmer who combines a wide range of tools to find the most meaningful data about website traffic. We trust his work and value it enormously.

Veronika Divišová, investigace.cz · Veronika’s profile on investigace.cz

Translated from Czech:

When it comes to data analytics, Marek is a geek in the best sense of the word. If he wants to know something, he explores it in depth. If I need to know something, I talk it through with Marek, because I couldn’t go into that level of detail on my own.

Josef Šlerka, investigace.cz · Josef’s profile on investigace.cz

Jobs.cz and Prace.cz: connecting product, UX and measurement

Worked with Tomáš Kafka from June 2018 to November 2020.

Tomáš and I worked on product analytics and improvements to individual parts of the products. Our shared starting point was data and an understanding of how people actually used the products.

To work with Mark is always a joy for me. He’s a pro, with a wit and overlap into many fields. Always knowledgeable and curious, Mark’s GTM scripts are a living demonstration of best practices.

Tomáš Kafka, Product Designer · Recommendation dated 11 November 2020 · Tomáš’s professional profile

Zonky: from measurement design to using the data

Worked with Ondřej Kašpar from February 2016 to July 2017.

At Zonky, my work covered measurement design, implementation support, data collection and processing, reporting and presenting findings. I also worked with the marketing and UX teams. Ondřej and I focused on developing the implementation and improving measurement quality.

He surprised me time and time again when he was able to pull the relevant reports seemingly out of nowhere and connect the dots where we were tracking “some data”, but incorrectly or inefficiently.

It was a pleasure to work with him on correcting occasional tracking errors, expanding the dataset and improving the quality of our setup.

Ondřej Kašpar, developer and development team lead · Recommendation dated 27 June 2017 · Ondřej’s professional profile

TrendLucid: data for business decisions

Worked with Honza Mayer in 2015 and 2016.

TrendLucid used data from the web to identify commercial opportunities when selecting products for online shops. Honza and I worked together on a project connecting analytics with decisions about product ranges.

Marek is one of the best online data analytics I’ve ever met. I seriously advise to work with him if your in deep data hole and have no idea how to get out.

Honza Mayer, CEO of TrendLucid · Recommendation dated 12 February 2019 · Honza’s professional profile

Further experience in analytics and development

At Creative Dock from 2016 to 2018, I designed and ran scalable analytics across multiple projects. As an external collaborator with Optimics in 2015 and 2016, I helped develop new web analytics tools.

Skills in practice

Measurement strategy and complex migrations

I designed and delivered the complete analytics workstream for a large international platform migration, from measurement strategy and the data model through documentation and collaboration with engineering teams to implementation and evaluation. The result was a smooth transition that preserved data continuity, traffic and business operations.

The project is described anonymously to respect the confidentiality of the engagement.

Implementation, diagnostics and data quality

I design measurement, help implement it, check the data being collected and investigate discrepancies. The work needs to connect with the questions a business is trying to answer. The Zonky project and Ondřej Kašpar’s recommendation above provide one example of this in practice.

Custom solutions and work across disciplines

I develop custom analytics scripts, methods and new approaches to measurement. I connect web analytics, development, SEO, UX, business and AI to solve problems that established methods alone cannot address. My AI work includes impact studies for international leadership teams, helping companies respond to change, and turning new capabilities into practical strategies, measurement and tools.

Using and measuring AI

I work on practical uses of AI, its effects on businesses and the measurement of AI visibility. I distinguish between bot visits, traffic from AI tools, citations and how a brand is described in generated answers. I explain my approach in a guide to measuring AI tools (in Czech).

This work also builds on my earlier experience with Word2Vec, search query analysis and automated query segmentation.

Collaboration and sharing knowledge

I work with developers, marketing, product and UX teams, leadership, legal teams and data protection officers. I explain technical problems in terms that fit the people who need to work with them. I help colleagues understand measurement and develop it further. Roman Hamrák’s recommendation above describes that everyday collaboration.

Google Analytics 4 certification

Google Analytics 4 Certification from Google. View my certifications on LinkedIn.

Tools and technologies

I choose tools according to the problem, the technical constraints and how the resulting data will be used.

Measurement and data analysis

  • Google Analytics 4, including GA4 360: measurement design and implementation, data validation, traffic analysis and reporting. My work with investigace.cz is one example of using GA4 in practice.
  • Google Tag Manager, including GTM 360 and server-side GTM: measurement implementation, custom tracking scripts and tag management. Tomáš Kafka’s recommendation also describes my work with GTM.
  • BigQuery: working with data exported from GA4 and building reporting on top of it. I use it when I need to go beyond the analytics tool’s interface.
  • Google Cloud and Snowflake: other platforms I work with on data projects.

Programming and custom solutions

I primarily work in Python, SQL and JavaScript. I also use R and other tools when a project calls for them. I build custom analytics scripts and automation for tasks that need their own design and validation. The dataLayer generator mentioned below is an example of work shared with the community.

AI stack and development environment

I use OpenAI models daily. I also regularly test Claude, Grok, Kimi and Gemini, other hosted models, and models with available weights, including running them locally.

For AI and development work, I use Codex, Claude, OpenCode and T3 Code. Visual Studio Code is part of my development environment. I also use GitHub Copilot in a corporate environment. Most of my projects are versioned and synchronised through Git.

I also use AI when developing custom solutions. I verify important outputs and remain responsible for professional decisions. The mix of tools evolves with their capabilities and the needs of the work.

Tools I have used in the past

I previously used Google Gemini CLI.

I also have experience with earlier generations of Google Analytics, including Universal Analytics and Enhanced Ecommerce. They are part of my professional history and my understanding of how measurement has evolved.

Articles and community contributions

Alongside recommendations from colleagues, my published methods, technical articles and community contributions offer a way to assess how I work.

Analytics and AI

Contributions documented elsewhere

More articles are available in the blog archive. I also share observations and professional updates on LinkedIn.

More about my work

About me covers my professional background and broader context. How I work explains my approach to collaboration. Services describes the kinds of projects I work on and the terms of an engagement.

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