Full-Stack Growth Builder at Joinfleek.com

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers.

She will pick the best candidates from Jack's network

The next step is to speak to Jack.

Job Title: Full-Stack Growth Builder, Retention & Lifecycle

Company Description: Joinfleek.com - Series B fashion-tech marketplace backed by a16z and Y Combinator

Job Description:
Join a high-velocity team reinventing the secondhand supply chain. As a Full-Stack Growth Builder, you will architect AI-driven CRM systems and lifecycle strategies from the ground up. You’ll own the entire retention engine, building dynamic tools and experimentation frameworks that move beyond static journeys to drive measurable, causal growth for thousands of global resellers.

Location: London, UK

Why this role is remarkable:

• Direct impact on sustainability by fixing the broken global supply chain for secondhand fashion, already saving 9 million items from landfills

• Work at a hyper-growth Series B startup that has raised ~$50M from premier investors including Andreessen Horowitz (a16z) and Y Combinator

• High-autonomy "super IC" role reporting to a VP of Growth (ex-Deliveroo) with the freedom to treat AI as your default development toolkit

What you will do:

• Architect and deploy adaptive, AI-powered CRM systems that determine optimal messaging, timing, and channels using real-time user signals

• Build end-to-end technical tooling for resellers, such as cross-listing features, to increase platform stickiness and long-term retention

• Design rigorous experimentation frameworks using causal inference and holdouts to quantify the true incremental impact of every growth initiative

The ideal candidate:

• A deeply technical builder who uses AI-native tools like Cursor or Claude Code to ship production-quality full-stack systems at high velocity

• Strong analytical fluency in SQL and experience navigating large, messy datasets to derive actionable insights and experimental results

• Proven background in growth or product engineering with a focus on building automated decisioning systems rather than just managing marketing campaigns

Who are Jack & Jill?
Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.

Next steps
Step 1. Visit our website
Step 2. Click 'Talk to Jack'
Step 3. Talk to Jack so he can understand your experience and ambitions
Step 4. Jack will make sure Jill (the AI agent working for the company) considers you for this role
Step 5. If Jill thinks you're a great fit and her client wants to meet you, they will make the introduction
Step 6. If not, Jack will find you excellent alternatives. All for free

We never post fake jobs
This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network.
Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description.
We appreciate this can make them look a bit suspect, but there isn't much we can do about it.
Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.