Full Stack Growth Builder

Methodfi; Greater London; On-site; GBP 60,000 - 80,000; Full time

Job summary

A leading technology firm in the UK is seeking a Full-Stack Growth Builder to enhance customer lifecycle marketing through innovative AI systems. The role involves designing smart CRM systems and leading experimentation efforts. Ideal candidates should have over 4 years of growth marketing experience, strong SQL skills, and a background in AI applications within CRM. This role is based in London and requires in-office presence initially, fostering teamwork and rapid decision-making.

Benefits

Flexible working after initial months

Strong team culture

Opportunities for professional growth

Qualifications

• 4-7+ years of lifecycle, CRM, or growth marketing experience.
• Hands-on experience with AI and automation in marketing.
• Deep expertise in experimentation and data analysis.

Responsibilities

• Own and optimize the consumer lifecycle strategy.
• Design and improve smart CRM systems using real-time data.
• Run rigorous experiments to gauge marketing effectiveness.

Skills

Lifecycle marketing

AI application in marketing

Experimentation frameworks

SQL

Systems design

Data analysis

Tools

Python

R

BigQuery

Snowflake

Job description

Can you help us fix the world's most broken supply chain?

The fashion industry produces over 100 billion garments a year. 60% end up in landfill, not because people don't want these clothes, but because the supply chain for getting secondhand fashion from donation to resale is completely offline, manual, and broken.

Fleek is fixing this. Our mission is to make secondhand the first choice. We are building the infrastructure powering the global secondhand clothing trade, through a B2B marketplace and the AI systems digitising the supply chain behind it.

Through Fleek, vintage stores, online resellers, and retail buyers source graded secondhand inventory directly from wholesalers and rag houses across multiple countries. Our key enabler is FleekSort, an AI model fine-tuned on secondhand fashion, that can grade, price, and categorise items with just a photo, turning what has historically been an opaque and manual trade into a structured, searchable, and tradable global inventory layer.

Since 2022, we have saved 9 million items from landfill and tripled in size year-on-year. We have raised ~$50M from a16z, Y Combinator, Burda Principal Investments, HV Capital, and others, and have recently closed our Series B. Our advisors and private investors include operators behind Depop, Shopify, and Postmates.

Today, we serve thousands of resellers and retailers across the UK, Europe, and the US. With the secondhand fashion market projected to reach $350B by 2027, Fleek is building the AI-native operational and financial backbone for secondhand commerce globally.

We are looking for people who want to build something that matters, and move fast doing it. Sound good? Keep reading.

About the Role

We are looking for a deeply technical, highly innovative Full-Stack Growth Builder to reinvent how customer lifecycle marketing drives growth at Fleek. This is not a traditional CRM role. You will architect the entire system, from data to strategy to execution, and treat AI as your default toolkit, not a nice-to-have.

You will design smart CRM systems that determine who to contact, when, through which channel, and with what message, using real-time user signals and context. You will build rigorous experimentation frameworks to quantify the true incremental impact of lifecycle messaging and prevent over-attribution. And you will lead the adoption of AI-powered content generation and personalisation, balancing scale with quality and relevance.

This is a marketplace scaling from thousands to tens of thousands of active buyers. The data infrastructure is being built in real time. If you get energy from building systems that learn, proving what actually works, and shipping at speed, this is the role.

What Makes You a Fleek Growth Builder?

• Systems Architect: You do not just run campaigns. You design adaptive systems that decide who to message, when, through which channel, and with what content, and that get smarter over time.

• AI-Native: You use AI as your default toolkit. Content generation, personalisation, segmentation, decisioning. You have built or implemented AI-driven systems, not just read about them.

• Experimentation Obsessed: You think deeply about incrementality, holdouts, causal inference, and marginal impact. You have caught campaigns that looked good on surface metrics but had no real value.

• Commercially Wired: You connect lifecycle outputs to business outcomes. You think in activation rates, retention curves, LTV, and revenue impact, not just open rates and clicks.

• Comfortable with Ambiguity: Fleek's growth data is complex and evolving. You thrive when the data is messy, the tracking is not perfect, and you need to find the answer anyway.

• Action-Oriented Communicator: You translate complexity into "here is what to do." Your stakeholders never have to guess what the data means.

• Startup Pace: You have worked in environments where speed matters, where you ship systems that drive same-week decisions, and where velocity is a competitive advantage.

What You'll Do

• Own the Consumer Lifecycle: Take full ownership of lifecycle strategy from onboarding and activation through engagement, retention, reactivation, and monetisation.

• Build Smart CRM Systems: Design and continuously improve systems that determine who to contact, when, through which channel, and with what message, using real-time user signals and context.

• Run Rigorous Experiments: Build and maintain experimentation frameworks to quantify the true incremental impact of lifecycle messaging. Use holdouts, lift tests, and causal inference to prevent over-attribution.

• Lead AI-Powered Personalisation: Drive the adoption of AI for content generation, personalisation, and decisioning. Balance scale with quality and relevance.

• Analyse and Surface Opportunities: Regularly analyse performance and experimental results to surface high-impact opportunities for activation, retention, and revenue.

• Manage Frequency and Trust: Establish best practices around frequency, fatigue management, and long-term user trust. Users should experience Fleek as relevant and well-timed, never noisy or generic.

• Build Reseller Tooling: Help build tooling for resellers end-to-end to drive retention and stickiness, such as cross-listing tools to go from Fleek to consumer marketplaces.

• Stay Ahead: Stay ahead of developments in lifecycle marketing, experimentation, and AI. Turn new ideas into production-ready systems.

• Use AI to Move Faster: Automate workflows, speed up analysis, and surface insights before anyone asks. You think about your role as a 10x-er through the lens of AI.

What You Bring

• 4-7+ years of lifecycle, CRM, or growth marketing experience. You have owned lifecycle strategy at a company where the systems you built directly impacted retention and revenue.

• Hands-on AI and automation experience. You have applied AI to content generation, personalisation, segmentation, or decisioning within CRM systems. Not theoretical, production.

• Deep experimentation expertise. Lift testing, holdouts, causal inference, incrementality. You have built experimentation frameworks, not just run A/B tests on subject lines.

• Strong SQL skills. You live in SQL and can pull, transform, and analyse large, messy datasets without waiting for someone else to build you a table.

• Experience designing adaptive systems. Rules-based, algorithmic, or hybrid decisioning systems that optimise messaging, prioritisation, timing, and frequency.

• Consumer or marketplace background. You have worked at a marketplace, ecommerce, or consumer company. You understand how activation, retention, and monetisation interact.

• Strong product intuition. You balance short-term optimisation with long-term customer trust and experience.

• Startup or scale-up experience. You have worked in environments with fast cycles, evolving data infrastructure, and high ownership.

Nice to Have

• Experience with Python or R for statistical modelling and analysis

• Familiarity with data warehousing tools (BigQuery, Snowflake, dbt)

• Experience building CRM/lifecycle infrastructure from scratch

• Background in building tools or internal products (not just campaigns)

Ready to build the lifecycle engine behind one of the fastest-growing marketplaces in Europe? If you want to architect systems that learn, prove what actually works, and ship at speed with a world-class team, we would love to hear from you.

How We Work

Fleek is an in-office company. We believe the best work happens when people are together, the quick decisions, the cross-functional energy, the ability to solve problems in real time. Most of the team works from our London HQ 3-4 days a week.

We are not prescriptive about it. Performance and trust matter more than attendance. For your first six months, we will ask you to prioritise being in the office, to learn the business, build relationships, and get up to speed. After that, you will have genuine flexibility to manage your own time. We hire adults and treat them accordingly.

The Practicalities

• Location: London HQ, Heneage Street, E1 (Shoreditch / Aldgate East)

• Work model: In-office, typically 3-4 days per week. Full-time in the office for your first six months, then genuine flexibility earned through trust and performance.

• Level: Senior

• Stage: Post-Series B, hyper-growth

• Team: 100+ across London, India, and Pakistan (~20 in London office)

• Culture: High ownership, non-hierarchical, fast-moving. Founder-led with strong opinions loosely held.

Our Values

Five values shape how we work at Fleek:

• Dream Big and Disrupt Yourself: Push the most ambitious version of what you are building. Step out of your comfort zone. Nothing is out of reach.

• Absolute Ownership: The buck stops with you. Drive initiatives to completion. Experiment, learn, persevere. The job is not done until the job is done.

• Curiosity Leads the Way: Do not accept anything at face value. Ask questions you do not know the answer to. That is how you innovate.

• Talk to the Customer: Deeply understand their challenges, motivations, and ambitions. Every decision starts with the customer at the centre.

• Embrace Diversity: A global team building for a global supply chain. Bring your authentic self and embrace the diversity of everyone you encounter.