Designing products that work for people and business.

I combine user research, data-driven experimentation, and strategic design thinking to create digital experiences that are both intuitive and effective.

Contact me LinkedIn

Case studies

4 projects
Project image
Marketplace 2024

Fotocasa: Online Real Estate Valuation Tool

Led the design of a free valuation tool that became a top organic entry point for Fotocasa, generating 40,000+ monthly visits and high-quality leads.

UX Research SEO Web
Project image
E-commerce 2023

Redesigning the registration flow to reduce drop-off

Placeholder — add your case study description here. Focus on the problem, the approach, and the measurable outcome.

Conversion Mobile Design System
Project image
CRO 2022

20% conversion uplift through data-driven UX audits

Placeholder — add your case study description here. Focus on the problem, the approach, and the measurable outcome.

Retail Data Workshops
Project image
Design System 2021

Building a scalable multi-brand design system from scratch

Placeholder — add your case study description here. Focus on the problem, the approach, and the measurable outcome.

Figma Tokens Scalability

Previous projects

Project image

Project title placeholder

Brief description of the project and its main outcome.

Company · Year

Project image

Project title placeholder

Brief description of the project and its main outcome.

Company · Year

Project image

Project title placeholder

Brief description of the project and its main outcome.

Company · Year

Testimonials

Let's work
together.

Whether you have a project in mind or just want to say hello — I'm always happy to talk.

How I approach design.

My process is structured to ensure every aspect of the project is considered, while maintaining flexibility to adapt to each challenge's specific needs.

How I work

Exploration & Discovery

Understand the problem, gather insights, and align with stakeholders to lay a solid foundation.

1.Understand the problem
2.Explore the landscape
3.Listen to users
Ideation & Validation

Generate design solutions, explore ideas, create prototypes, and gather feedback to refine the direction.

4.Generate initial solutions
5.Validate internally
6.Validate with users
Delivery & Development

Implement the design, ensure quality, and monitor the product post-launch to ensure its success.

7.Prepare for implementation
8.Ensure quality
9.Close the loop

Exploration & Discovery

Understand the problem, gather insights, and align with stakeholders to lay a solid foundation.

1.

Understand the problem

Lay the foundation by clearly identifying the business objectives and user needs.

  • What problem are we solving?
  • What opportunities emerge from the challenge?
  • What are the business goals we're trying to achieve?
  • How do we prioritise ideas and features to implement?
  • What are the user needs and pain points we must solve?
  • Which stakeholders should be involved in the process?
  • What data or insights do we already have about this problem?
  • Which metrics or KPIs should we focus on?
  • What hypotheses do we need to validate or invalidate?
Stakeholder alignment and problem framing

CSAT insights for the pro tool.

2.

Explore the landscape

Look outward to gather inspiration and understand the wider impact across the organisation.

  • Benchmarking: Reviewing existing solutions in the market to understand trends and best practices.
  • Stakeholder Interviews: Gathering insights from internal teams to understand vision, goals, and constraints.
  • Technical and Business Considerations: Assessing feasibility and business priorities.
  • Cross-Functional Collaboration: Engaging with teams across disciplines to ensure alignment and incorporate diverse perspectives (Marketing, SEO, Legal).
Competitive benchmarking and market analysis

Comparative between Fotocasa and Idealista.

3.

Listen to users

Dive into user research to uncover pain points, unmet needs, and expectations.

  • User Interviews/Surveys: Talking directly with users to uncover needs, pain points, and frustrations.
  • Synthesising Findings: Presenting research findings to stakeholders, product teams, and UX teams to ensure alignment.
Image placeholder

Ideation & Validation

Generate design solutions, explore ideas, create prototypes, and gather feedback to refine the direction.

4.

Generate initial solutions

Start shaping ideas through collaboration and rapid exploration.

  • Collaborative Ideation with the Product Team: Aligning with development to understand their concerns and vision for functionality.
  • Initial Design Proposals: Creating early-stage concepts and prototypes based on research insights.
  • Assess feasibility with product and tech teams.
Early ideation and solution exploration

Participatory design example using Miro.

5.

Validate internally

Test the first ideas internally to refine direction before involving users.

  • Iterative Design: Creating multiple prototypes based on feedback, refining them into more polished solutions.
  • Design Critiques: Presenting ideas to the team and stakeholders to gather early feedback. Critiques often help identify blind spots or better solutions early in the process.
  • Feedback Integration: Continuously integrating feedback from stakeholders to refine the design. This is where the solution begins to take shape, preparing it for real-world testing with users.
Validate internally — design critiques and feedback

Prototype created to test a specific functionality.

6.

Validate with users

Put designs in front of users to test assumptions and identify improvements.

  • Usability Testing: Testing prototypes with users to validate design decisions and gather real feedback.
  • Feedback Loop: Iterating on designs based on user feedback to improve usability and satisfaction.
  • Final Validation: Reviewing the design with key stakeholders and the development team.

By the end of this phase, the solution should be validated and ready for development.

Image placeholder

Delivery & Development

Implement the design, ensure quality, and monitor the product post-launch to ensure its success.

7.

Prepare for implementation

Finalise a robust solution that's consistent, accessible, and ready for development.

  • Scalability & Modularity: Ensuring the design is flexible and scalable for future growth.
  • Design System & Consistency Check: Ensuring adherence to the design system for consistency.
  • Accessibility Check: Verifying compliance with accessibility standards to accommodate all users.
  • Edge Cases & Empty States: Ensuring all scenarios are covered and the solution functions across various use cases.
  • Phased Development: If necessary, breaking down the development into stages to ensure quality and timely delivery.
  • Handoff: Preparing all necessary assets, documentation, and design specifications for the development team.
  • QA: Collaborating closely with the development team during pre-production to resolve any issues early.
Image placeholder
8.

Ensure quality

Support development with attention to detail and data-driven validation.

  • Final QA in Production: Ensuring everything works as expected after launch.
  • A/B Testing: If applicable, setting up A/B tests to validate hypotheses with key metrics.
  • Metrics Tracking: Monitoring key metrics to measure the success of the launch and identify areas for improvement.
Image placeholder
9.

Close the loop

Follow up post-release to track impact, detect opportunities, and plan improvements.

  • Identifying UX or Technical Debt: Recognising areas that need further refinement or optimisation.
  • Future Phases Documentation: If it's an MVP, documenting the roadmap for future enhancements.
  • Metrics Follow-up: Continuously monitoring metrics to ensure the product meets its goals.
Image placeholder

Let's work
together.

Whether you have a project in mind or just want to say hello — I'm always happy to talk.

Design is about making things work.

9+ years working across complex digital products — from marketplaces and e-commerce to global retail platforms. I specialise in UX research and A/B experimentation, always connecting user needs with measurable business outcomes. Currently based in Barcelona, open to remote opportunities.

Contact me LinkedIn
Karlos Zarzu with the Adevinta Real Estate UX Team

Adevinta Real Estate UX Team

Experience

Jan 2022 — Mar 2026

Adevinta · Fotocasa Group

Senior Product Designer

  • End-to-end design leadership in high-traffic squads (Fotocasa and Habitaclia), executing an A/B testing roadmap that optimised lead generation and significantly improved the reliability of the registration flow.
  • Reduction of technical uncertainty through Continuous Discovery frameworks, transforming qualitative and quantitative insights into high-value product opportunities for Web and App ecosystems.
  • Evolution and active contribution to global design systems (SUI and Panot) through the implementation of tokens, optimising handoff efficiency and ensuring visual consistency in a multi-brand architecture.
  • Strategic collaboration with C-Level profiles, Product Managers, and Tech Leads, facilitating workshops that unified the long-term product vision and ensured compliance with accessibility standards.

Nov 2020 — Jan 2022

Flat 101

Senior UX/UI Designer & CRO Specialist

  • Management of audits and execution of data-driven A/B tests for the Retail and Insurance sectors, achieving a 20% increase in conversion rates for key accounts.
  • Creation of Design Systems that reduced development time, standardising documentation and UI Kits to optimise the handoff process.
  • Product lifecycle leadership for multiple simultaneous accounts, resulting in a 12% increase in service contracting (upsell) due to the demonstration of measurable results and ROI.

Mar 2020 — Oct 2020

Desigual (via Flat 101)

Senior UX Designer & Researcher

  • UX/UI design management for global events (Black Friday and Mid-Season), ensuring frictionless checkout flows and total alignment with brand guidelines.
  • Improvement of mobile engagement through user and stakeholder research, transforming qualitative insights into product iterations.
  • Development of high-fidelity prototypes for complex digital products to ensure success in the launch of new functionalities.

Jan 2019 — Mar 2020

Interactius

UX Designer & Researcher

  • Comprehensive management of Research phases and definition of complex information architectures, achieving greater precision in navigation redesign for critical sectors such as banking and security.
  • Management of the full product cycle and direct communication with clients, facilitating Design Thinking and Google Design Sprint workshops to align stakeholders with the project vision.
  • Implementation of workflows based on prototyping and constant validation, ensuring the delivery of scalable MVPs for sectors such as Banking, Surveillance, Startups, Sports, E-commerce.

Jul 2018 — Jan 2019

Bershka · Inditex

UX & UI Product Designer

  • Creation of the Design System based on Atomic Design for the new global platforms (Web, iOS, Android).
  • Design and iteration of personalised UI modules through A/B tests within the Personalization team, using metric analysis to increase user retention.
  • Facilitation of Design Sprint and Design Thinking workshops for the ideation of new functionalities.
Download CV

How I work

Exploration & Discovery

Understand the problem, gather insights, and align with stakeholders to lay a solid foundation.

1.Understand the problem
2.Explore the landscape
3.Listen to users
Ideation & Validation

Generate design solutions, explore ideas, create prototypes, and gather feedback to refine the direction.

4.Generate initial solutions
5.Validate internally
6.Validate with users
Delivery & Development

Implement the design, ensure quality, and monitor the product post-launch to ensure its success.

7.Prepare for implementation
8.Ensure quality
9.Close the loop
See full approach

Let's work
together.

Whether you have a project in mind or just want to say hello — I'm always happy to talk.

© 2026 Karlos Zarzu

Barcelona · Available for remote

Released

Fotocasa Valuation Tool

Hero image placeholder

Overview

Fotocasa's Online Real Estate Valuation Tool offers users an instant, free estimate of a specific property's market value. Whether they're planning to sell, rent, or buy, this tool empowers users to make more informed decisions by giving them quick access to real-time market insights based on data.

As the Product Designer, I led this feature from scratch in close collaboration with the SEO team. We focused on creating a well-structured, content-rich landing page optimised for search engine indexing, while designing a fast and intuitive valuation flow to maximise user conversion.

Feature

Online Real Estate Valuation Tool

Role

Q1 2024 · Product Designer

Skills

Product design · User research & testing · Stakeholder management · Cross-functional collaboration

Key stakeholders

Management, SEO, Monetisation, Datavenues

Link

fotocasa.es/tasacion-online ↗

Problem to solve

This feature wasn't designed to solve a specific user problem — similar tools already existed in the market. Instead, it aimed to seize a strategic opportunity. The SEO and Monetisation teams developed a business case showing that a free property valuation tool could serve as a powerful driver of organic traffic in the short term.

In the longer term, the tool would help generate high-quality leads — users considering selling or renting their homes — for real estate agencies, aligning perfectly with Fotocasa's marketplace model.

Key challenges

  • SEO vs. UX: Creating a content-rich landing page without harming user flow or conversions.
  • Simplifying complexity: Turning valuation logic into a fast, user-friendly experience.
  • Trust: Conveying reliability despite being an automated estimate. We addressed this through transparent copy and clear visual communication.
  • Lead generation: Optimising for lead generation without adding friction to the experience.

Approach

Exploration & Discovery

We began with competitive benchmarking to understand how similar tools positioned themselves in the market. Alongside that, we assessed technical constraints and business priorities, aligning closely with SEO and Monetisation teams. Early cross-functional collaboration helped define scope, value proposition, and success metrics.

Ideation & Validation

We explored different flows and UI directions through iterative design, gathering early feedback via design critiques. Prototypes were tested through remote usability testing using UserZoom, which allowed us to validate assumptions and identify pain points. Feedback loops were short, enabling us to quickly refine the experience.

Delivery & Development

We delivered a polished, accessible, and scalable solution, covering edge cases and preparing thorough documentation for smooth handoff. The launch was supported by close collaboration with development and QA teams, ensuring the experience worked seamlessly across web and mobile platforms.

Process image placeholder

Solution & Impact

Final solution image placeholder

Overview of the valuation flow.

We launched a unified valuation tool that blended SEO-rich content with a frictionless conversion flow. The landing page became a top organic entry point for Fotocasa, while the tool itself helped convert visitors into qualified leads for real estate agencies — directly supporting the marketplace monetisation strategy.

After phase two, the tool started generating high-quality leads by connecting homeowners with real estate agencies, meeting the secondary goal of monetising the valuation tool.

Impact

  • Organic Traffic Growth: The tool contributed to Fotocasa's strong SEO presence, with the domain receiving an estimated 40,000 organic visits per month.
  • Strong SEO Positioning: Ranks on the first page of Google for highly competitive keywords such as "valoración online", "tasación online", "valoración gratuita", and "valoración de vivienda".
  • Lead Generation: After phase two, the tool started generating high-quality leads by connecting homeowners with real estate agencies.

Let's work
together.

Whether you have a project in mind or just want to say hello — I'm always happy to talk.