Build the category, don’t just work in it.
Arithmos is building the retail layer for direct indexing. We turn a plain-English idea into a transparent, rule-based portfolio with institutional-grade backtesting and analytics — making structured investing accessible to millions rather than the top 0.1%. We are hiring a small number of senior founding-team roles to take us there.
Open roles
8 live- founding·Engineering·London (hybrid) or Remote (UK/EU)·Full-time
Frontend / Product Engineer (Founding)
Own the product surface that millions of people will use to build their first custom index.
£150,000–£170,000 base · 1.0%–1.5% equity · performance bonus - senior·Research·London (hybrid) or Remote (UK/EU)·Full-time
Data / Quant Engineer
Build the back-testing engine and portfolio-construction intelligence that every Arithmos claim depends on.
£200,000–£220,000 base · 1.5%–2.0% equity · performance bonus - lead·Solutions·London (hybrid)·Full-time
Head of Custom Index Solutions
Define a new category in retail investing. Own the investment thesis that everything else hangs off.
£280,000–£310,000 base · 3.0%–4.0% equity · significant performance bonus - senior·Engineering·London (hybrid) or Remote (UK/EU)·Full-time
Platform / Backend Engineer
Own the data fabric, scheduling, and cache layers that keep every backtest reproducible and every page sub-second.
£170,000–£200,000 base · 0.75%–1.25% equity · performance bonus - founding·Design·London (hybrid) or Remote (UK/EU)·Full-time
Founding Product Designer
Define the visual + interaction language for retail direct indexing. From OG cards to the prompt-to-portfolio flow.
£130,000–£160,000 base · 0.75%–1.25% equity · performance bonus - senior·Growth·Remote (UK/EU) or London (hybrid)·Full-time
Growth Engineer (SEO + Lifecycle)
Run the growth loop — programmatic SEO, lifecycle email, and conversion experiments — end to end.
£140,000–£165,000 base · 0.5%–1.0% equity · performance bonus + revenue-tied bonus - intern·Operations·London (hybrid) or Remote (UK/EU)·Internship · 10–12 weeks (summer)
MBA Summer Intern (Generalist)
Spend a summer at a venture-backed fintech founding team — own a real workstream from week one.
£108,000–£132,000 base · — equity · £9,000–£11,000 monthly stipend · return-offer bonus on conversion to full-time - intern·Research·London (hybrid) or Remote (UK/EU)·Internship · 10–12 weeks (summer)
MBA Finance Intern (Index Research & Methodology)
Help us build the index methodology that retail investors will use to allocate billions — under the eye of a founding research team.
£120,000–£144,000 base · — equity · £10,000–£12,000 monthly stipend · return-offer bonus on conversion to full-time
How we work
- Small team, high trust. Everyone owns a surface end-to-end. No layer of managers between you and the thing you’re building.
- Ship weekly. Every Friday something new is live. Feature flags and careful instrumentation over multi-quarter roadmaps.
- Institutional rigour, retail clarity. We care deeply about backtest honesty and metric reproducibility — and just as deeply about someone understanding their index in thirty seconds.
- Meaningful equity. Every role includes a real equity stake. Bands are public (in each role spec) and not negotiable after offer — the offer is the offer.
Apply
Pick a role (or select “Other / speculative” if none of them fit) and attach your CV. We’ll always read a thoughtful speculative application — if you’re exceptional in fintech, quant research, infrastructure, or growth, tell us what you’d want to own.
