Site Reliability Engineer at High Growth B2C Startup

Gizmo is an AI startup on a mission to make learning so easy that anyone can learn anything. We're building Duolingo for anything - a platform that uses gamification and social mechanics to make learning fun.

With over 1 million monthly active users and $4M in annual recurring revenue, we're already one of the fastest-growing startups in the UK. Backed by leading investors, we recently raised $16M in Series A funding to accelerate our vision of helping 1 billion people learn.

Role Overview
Reporting to the founders, you will own capacity, performance and reliability for Gizmo's full-stack platform as daily traffic climbs from hundreds of thousands to millions of users. You'll write code across the stack, but your charter is classic SRE: defend SLOs, eliminate toil, and raise the ceiling on scale before it becomes a hard limit.

Key Responsibilities

• Define SLIs/SLOs for latency, availability and error rate; codify error budgets and partner with product teams on trade-offs.
• Perform load-testing, capacity modelling and up-front scalability design for PostgreSQL, OpenSearch, Redis, Hasura and CF Workers; produce data-driven scaling plans.
• Extend metrics, structured logging and tracing; establish alert rules that page only on user-visible impact; build actionable runbooks.
• Join the on-call rotation, lead blameless post-mortems, drive remediation work to closure and track MTTR/MTBF improvements.
• Automate repetitive ops on Kubernetes and CI/CD; keep "toil"
• Coach full-stack engineers on query optimisation, schema design and back-pressure techniques; document patterns and anti-patterns by creating an SRE playbook

• Hands-on scale experience: you have run relational stores at 100 k+ TPS or 1 M+ concurrent users (e.g., multi-tenant PostgreSQL, sharded MySQL).
• Strong backend fundamentals around concurrency, caching, indexing and distributed systems trade-offs.
• Proven track record of setting SLOs, building dashboards (Prometheus/Grafana, OpenTelemetry, etc.) and tuning alerts.
• Comfort with Kubernetes, IaC and cloud-native patterns; can debug from network to application layer.
• Start-up bias for action: you prioritise high-leverage fixes, ship iteratively and own outcomes end-to-end.
• Collaborative and feedback-driven; you welcome post-mortem culture and continuous improvement.
• Driven by impact - you prioritise work that moves the needle!

Nice-to-haves: experience with Hasura internals, Cloudflare Workers edge optimisation, or running OpenSearch clusters at scale.

• Highly competitive salary.
• You'll own a piece of what you're building - equity included.
• Hybrid working model with 4 days in the London Liverpool Street office.
• The opportunity to become one of the earliest employees in one of the UK's fastest-growing startups.
• Private health insurance