Arithmos
Multi-provider data fabric
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Arithmos
Platform / Backend Engineer
Own the data fabric, scheduling, and cache layers that keep every backtest reproducible and every page sub-second.
London (hybrid) or Remote (UK/EU) Full-time £170,000–£200,000 base
0.75%–1.25% equity 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
You will own the platform that every other surface depends on — the multi-provider market-data fabric, the backtest cache, the scheduled rebalance jobs, and the integrity guarantees that make our claims defensible.
What you’ll do
Multi-provider data fabric
- Add new providers to the fall-through chain
- Tighten survivorship-bias controls and currency normalisation
- Tame upstream rate-limits and observability gaps
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Cache, queue, and scheduling layers
- Make first-paint and first-backtest sub-second on cold cache
- Bound concurrency on the LLM agent + backtest workers
- Replace the cron + revalidate hacks with a real durable layer
Reliability + integrity
- Hash-chained backtest verification harness
- Per-provider golden-path smoke tests
- Tracing, alerting, and SLOs that actually fire
Requirements
- 5+ years building production backend systems on the JVM, Go, Node, or Python
- Deep PostgreSQL experience (query plans, partitioning, lock contention)
- Comfortable owning a service from first commit to on-call rotation
- Strong API design — internal and external
Nice to have
- Worked on financial market data, exchange data, or quote books
- Built durable workflow / queue systems (Workflow DevKit, Inngest, Temporal)
- OpenTelemetry / structured-tracing experience
Why this role is exceptional
- Real impact on every page-load and every claim we make
- Greenfield areas (durable workflows, mTLS broker integrations)
- Founding equity tier on a product with clear PMF signal
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Compensation & Benefits
- £170,000–£200,000 base
- 0.75%–1.25% equity
- performance bonus
- Private healthcare
- 25 days holiday + bank holidays
- Top-tier equipment
- 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 Platform / Backend Engineer
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Arithmos is an equal-opportunity employer. Published 7 May 2026.
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