Arithmos
Own the end-to-end frontend experience
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Frontend / Product Engineer (Founding)
Full-time
Open role
Arithmos
Own the product surface that millions of people will use to build their first custom index.
Location: London (hybrid) or Remote (UK/EU)
Position type: Full-time
Salary: £150,000–£170,000 base
Equity: 1.0%–1.5%
Bonus: Performance bonus
About Arithmos
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. Our goal is to make structured investing accessible to millions.
The Role
This is a founding product engineer role. You will own the user experience that determines whether users understand, trust, and share what we’ve built. Your work directly impacts growth, activation, and revenue.
What You’ll Do
- Own the end-to-end frontend experience
- Index creation flow (prompt → portfolio → backtest)
- High-performance charting and data visualisation
- Public, shareable index pages
- Build growth-critical features
- “Clone this index”
- Performance comparisons vs benchmarks
- Social sharing and embedding
- Drive conversion and activation
- Reduce time to first index
- Improve clarity of outputs (performance, holdings, risk)
- Partner with growth on rapid experiments
- A/B tests on onboarding, UI, and messaging
- Ensure best-in-class performance
- Sub-second load times
- Smooth, responsive UI across devices
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Requirements
- 3–7+ years building high-quality web products
- Strong in React / Next.js / TypeScript
- Experience with data-heavy UIs (charts, dashboards, analytics)
- Product mindset: you care about user behaviour, not just code
- Ability to ship quickly and iterate under ambiguity
Nice to Have
- Experience in fintech / investing products
- Familiarity with charting libraries (D3, Recharts, TradingView, Highcharts)
- Experience building viral or consumer-facing products
Why This Role Is Exceptional
- Direct ownership of a category-defining product
- Massive upside via equity
- Work on a product with clear product-market fit potential
- Build something users actually use daily — not internal tools
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Compensation & Benefits
- Base salary: £150,000–£170,000
- Equity: 1.0%–1.5%
- Bonus: Performance bonus
- Private healthcare
- 25 days holiday + bank holidays
- Top-tier equipment (M-series MacBook, studio monitor, whatever you need)
- Flexible working
- Annual company offsite
How to Apply
Upload your CV and a short note — no more than 200 words — on why this role in particular. If you have work you’re proud of that’s relevant (a product you shipped, a research paper, a backtest you ran), link to it. Two-stage process: screening call, then a take-home + technical deep-dive with the team you’d join.
Applying for Frontend / Product Engineer (Founding)
- Your name
- LinkedIn (optional)
- Portfolio / recent work (optional)
- Why this role (≤200 words)
- CV (PDF, DOC, DOCX, TXT or RTF — max 5 MB)
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Arithmos is an equal-opportunity employer. Published 24 April 2026.
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