Lead Growth Engineer in London

The basics

Your title will be Growth Engineer. Kameron, Senior Growth Engineer, is the hiring manager. We work Mon-Thu in our office in Chancery Lane, London, Fri from anywhere.

What are we building?

Walk around the average office and you’ll see people’s days taken up by emails, Slack and meetings instead of real work. People in client facing roles - think estate agents, insurance brokers, recruiters - feel this pain most acutely. Instead of meeting clients, they spend hours doing admin. Following up. Scheduling meetings, then taking notes on them. Answering questions they’ve been asked a thousand times. Sorting through the mess that is their inbox.

We’ve built an AI executive assistant that looks at all your emails, messages and meetings, and uses that knowledge to answer your email, schedule meetings, take next steps from meetings and organise your inbox.

How has it been going?

This year, we’ve grown from $1M to $30M ARR, with a technical team of just 12 (up from 2). We’re forecasting $100M ARR by the end of 2026. We have product–market fit, and we take none of it for granted. We’re relentlessly focused. There will be a $10B+ company in this space. It will be us if we stay focused. Ranked 7th in Andreessen Horowitz’s list of top AI apps, based on real startup spend data. The other nine in the top 10 are valued at $10B+.

What do we value?

Autonomy, agency, and ownership. Each of our Growth Engineers owns one of Fyxer growth loops - whether that be a viral loop within a product, or an onboarding, monetisation or referral journey. They own both the strategy (we have no product managers and have no plans for that to change) and the execution of that strategy. They choose when to bring in qualitative data (customer interviews, surveys etc) and quantitative, supported by our data engineering department.

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 does mean you’ll need to bring an intensity to this role that might not be asked at other companies. But it also means you will be fast tracked into more senior roles and responsibilities far earlier.

What will I do?

In short, you’ll be expected to come up with and entirely own implementing your experiment ideas to improve product-led growth at Fyxer. Although you’ll be working alongside other growth engineers, this role requires a lot of independence and self-management to come up with ideas and execute them. You’ll use data from Metabase, BigQuery, and PostHog to generate new ideas, analyse your experiments, and prioritise your backlog.

What does our ideal hire look like?

• Must have:

• Thorough understanding of TypeScript and React.
• Can function as a full-stack engineer (leaning heavily towards front-end development), working on both client and server-side code, answering data questions using SQL, and contributing to DevOps and CI/CD processes.
• Core growth skills including data analysis, UX design, and product development, combined with a passion for marketing and conversion psychology to ideate and build high-impact experiments.
• A sense of urgency and intensity in your work.

• Worked at an early-stage tech company as an engineer.
• Keen interest in LLMs, workflow automation, and AI agents.
• Previous experience as a growth engineer or as a software engineer in a growth team, or you’ve demonstrated through self-driven work any of the following: optimising customer journeys, building virality/seat expansion/referrals, or building revenue operations infrastructure.
• Knowledge of the typical B2B SaaS growth/revops stack—experimentation, CRM, segmentation tools.
• A deep understanding of product growth mechanics. You think in terms of growth/habitual loops and network effects rather than just funnels. You’re comfortable using multivariate testing and correlative analysis to shorten time-to-value and identify the early indicators of long-term retention.

Our tech stack

Broadly, we use a fairly typical serverless Typescript stack. It’s not a requirement to have worked with every tool in this stack, but the more the better:

• Typescript for all production code
• Firestore as our production database
• Firebase Auth as our auth system
• Backend deployed on Firebase Functions, and making use of PubSub and Cloud Storage
• React frontend, using ShadCN for components, TailwindCSS for styling, React Query for state management
• Posthog for frontend analytics (events, sessions)
• Growthbook for product experimentation (feature flags, experiments, bandits)
• BigQuery as our data warehouse, with Metabase for data visualization. Production data and Posthog events both stream into it so data is in one place.
• Sentry and Google Cloud Logging for monitoring
• Github Actions for CI/CD
• Cursor/Claude Code/OpenCode setup for each engineer in the team.

The application process

Submit your CV (no need for a cover letter). Initial call with someone from the Fyxer team to review your experience and motivation and a small 10 min paired programming challenge (30 mins). Experience interview with one of our growth engineers (30 mins). Practical interview (1hr): Wireframe an experiment and talk us through your thinking (30 mins). Live coding exercise (30 mins). Meet Richard, CEO (30 mins).