Staff Data Scientist - Experimentation

September 22, 2026

Hybrid

Lead

Barcelona, Spain

Important before applying

This job has conditions that may affect your decision to apply

Mandatory office attendance

Description

Wallapop is a Barcelona-based scale-up running a second-hand marketplace across Spain, Italy and Portugal. The company is looking for a Staff Data Scientist - Experimentation to own and evolve its company-wide experimentation practice. The role combines hands-on statistical expertise with coaching Product teams and shaping experimentation standards, governance and tooling for marketplace growth. Work follows a hybrid model based in Barcelona with at least six days per month in the office.

Responsibilities

Define Wallapop's experimentation vision and roadmap and establish company-wide standards
Create frameworks for experiment prioritization and develop guardrail metrics and governance
Own experimentation methodology across the company and introduce advanced techniques such as CUPED, sequential testing and network effect measurement
Act as a strategic advisor and coach to Data Analysts, Data Scientists and PMs on hypothesis development, experiment design and success metrics
Build Wallapop's experimentation curriculum and deliver training programs for PMs, Designers, Engineers and Analysts
Partner with Data Engineering and Analytics Engineering to improve infrastructure
Evolve Amplitude Experiment data practices and define quality standards for exposure logging
Design experimentation approaches for search ranking, recommendations, personalization, marketplace liquidity, supply-demand dynamics, seller growth, trust & safety and ads monetization

Requirements

8+ years of total experience in data science, product analytics, or causal inference, including at least 4 years deeply focused on experimentation
Strong SQL proficiency along with experience using Python or R
Expertise in experimental design, statistical inference, A/B testing, and variance reduction
Proven ability to partner directly with Product organizations and influence senior stakeholders using strong business judgment
Demonstrated success building experimentation cultures and experience coaching PMs and analysts
Excellent communication skills
Experience with Amplitude as a plus
Experience in marketplaces, e-commerce, consumer internet, or two-sided platforms as a plus
Experience with recommendation systems or search systems as a plus

Conditions

Hybrid model with a minimum of 6 days per month in the office
All roles are Barcelona based
Generous individual learning budget of 2K per year
Free office meals with lunch selection from different providers
Group and individual English, Catalan and Spanish lessons during the working day
Private Health Insurance with Alan
Flexible working hours plus intensive Fridays
Flexible remuneration to deduct from gross salary (kindergarten, food, transport)
Gym and Wellness plan, including a physiotherapist in the office
Relocation package with monetary support and legal advice, plus visa sponsorship when applicable
26 holidays per year
TOP hardware of your choice (latest Apple or Windows)

SQLPythonRA/B testingexperimental designcausal inferenceCUPEDsequential testingvariance reductionmarketplace / e-commerceAmplitudeAmplitude Experimentmarketplaces

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