Lead Growth Engineer
THE BASICS
This role pays up to £170k/year DOE + equity
Reporting to: Head of Growth Engineering
Location: Chancery Lane, London — Mon–Thu in office, Fri WFH
WHAT ARE WE BUILDING?
Fyxer is an AI Email & Meeting Assistant that eliminates admin burden for professionals in client-facing roles — think sales, consultants, recruiters. We understand your inbox, draft replies in your own voice, and take crisp meeting notes.
We’re a pure-play applied AI company — not a SaaS product with AI bolted on. We use fine-tuned open-source models, tool use, and retrieval-augmented generation. Users send 53% of the email drafts we generate.
Since launching in March 2024, we’ve grown from $0 to $30M+ ARR. We raised a $10M Series A and a $30M Series B in under 18 months. Our backers include Marc Benioff (Salesforce), Harry Stebbings (20VC), David Singleton (ex-CTO of Stripe), and Madrona (first investors in Amazon and Snowflake).
THE ROLE
We’re hiring a Lead Growth Engineer to sit within our Growth Engineering team — a small, high-ownership group responsible for the product-led growth loops that drive Fyxer’s explosive revenue trajectory.
This isn’t a UI polish role. You'll own the infrastructure and strategy that drive growth from session to conversion. This means designing and running A/B tests, analyzing user behavior data, and optimizing every step of the acquisition journey across our paid landing pages programmatic SEO, and lead magnet micro-apps .You’ll work at the intersection of data, marketing, product, and engineering — using rigorous A/B testing, behavioural analytics, and a deep understanding of B2B SaaS growth mechanics to move the metrics that matter.
Each Growth Engineer owns an area of the product end-to-end. No PMs. You own the strategy and the execution.
WHAT YOU’LL OWN
Lead our conversion rate optimisation programme across the full user journey — from landing page to paid activation and seat expansion
Design, build, and run multivariate experiments to systematically improve conversion rate and identify through data ways to improve our sign up quality for long term retention.
Own the experimentation infrastructure: testing frameworks, statistical rigour, result interpretation, and rollout decisions
Work with quantitative data (product analytics, revenue data) and qualitative data (customer interviews, session recordings) to identify the highest-leverage opportunities
Build features and flows — this is a full-stack engineering role, not just configuration of tools. You’ll ship code.
Contribute to Fyxer’s growth loop strategy: virality, referrals, seat expansion, and upgrade mechanics
Collaborate with Marketing to align product-side CRO with paid and organic acquisition funnels
WHAT WE’RE LOOKING FOR
You’re an exceptional engineer who thinks in growth loops and conversion mechanics, not just funnels.
Previous experience as a CRO, growth, or software engineer with a track record of measurably improving conversion across sign-up, onboarding, or monetisation flows
Is details oriented with an eye for design and UX. Has worked with CSS/React animations before and is comfortable with larger experiments and projects.
A deep, intuitive understanding of consumer psychology and why certain words or layouts get customers to take action.
Comfortable designing and interpreting multivariate tests and correlative analyses; you know the difference between statistical significance and practical significance
Proficient in our stack (or close to it): TypeScript, React, Next.js, TailwindCSS, ShadCN, React Query, serverless functions
Knowledge of the B2B SaaS growth and experimentation stack: feature flagging, CRM integrations, event tracking, segmentation tools
AGI-pilled, you love AI and want to try and automate as much as possible within your role and across the organization.
You bring intensity. We’re a small team and expect genuine ownership — this isn’t a place where you wait to be told what to test next
Comfortable moving between quantitative rigour and qualitative instinct — you know when to run an interview and when to run a query
NICE TO HAVE
Experience with session recording tools (Hotjar, FullStory, PostHog), funnel analytics platforms, and product event tracking pipelines
Familiarity with LTV modelling, cohort analysis, and churn prediction
Experience with AI-assisted development workflows (Cursor, Claude Code, or similar)
Prior experience at a fast-growing B2B SaaS or AI startup
THE CONTEXT
We’re very intentional about adding new people. We think a small team of exceptional people working hard at a problem they care about will always beat a larger, less focused team.
That means you’ll need to bring an intensity to this role that might not be expected at other companies. But it also means you’ll be fast-tracked into more senior roles and responsibilities far earlier.
We also believe in hiring people who want ownership and autonomy in their work — and giving it to them. Farm to table: you nurture the crops, assemble the plates, we just loan you the land.