Sr. Platform Engineer

About Onedome

We're a UK fintech building high-throughput digital infrastructure for the mortgage and property space. Recently acquired Trussle. We're taking our platform to the next level: fully automated, self-healing, observable, and built to handle real traffic spikes (we have a TV launch coming up).

The role

You'll be our senior platform engineer. Not a traditional ops role. You'll treat infrastructure as a product, build the internal developer platform our engineers deploy through, and bring SRE discipline into the application tier when it's needed.

You won't have a platform team to lean on. You'll be building that capability. We know exactly what we need.

What you'll do

• Own 5 AWS accounts across the organisation (QA, Prod, Infra, plus two others)
• Architect and maintain infrastructure as code with Terraform. Replace the click-ops that's still around
• Stand up CI/CD pipelines engineers actually want to use. Blue/green and canary where it makes sense
• Run releases reliably and reduce key-person risk on the deploy process
• Set up monitoring, alerting, and incident response so we catch issues before customers do. Define SLIs and SLOs that map to real user journeys
• Lead incident response as the primary infra responder. Run blameless post-mortems
• Patch and harden the platform. We're a fintech, this matters. IAM least privilege, secrets management, vulnerability scanning, MFA enforcement
• Lead infrastructure work for the TV launch: traffic spikes, autoscaling, capacity planning, runbooks
• Partner with backend engineers when production issues cross into the app tier. JVM tuning, connection pools, async patterns, memory leaks
• Architect multi-region DR. Drive the platform toward self-healing
• Optimise cost across DynamoDB, Lambda, and the wider AWS footprint
• Set architectural guardrails with tech leads and SWEs. Mentor engineers as the platform capability grows

You must have

• 6+ years hands-on AWS in production (VPC, IAM, EC2/ECS/EKS, Lambda, S3, CloudFront, Route53, RDS, DynamoDB, SQS)
• Production Terraform (Terragrunt a plus). Multi-environment state management
• Production Kubernetes and Docker. EKS specifically
• Strong CI/CD experience: GitHub Actions, GitLab, Jenkins, or ArgoCD. GitOps practices
• Strong infrastructure security: IAM least privilege, secrets, patching, vulnerability scanning, MFA enforcement
• Observability from scratch: CloudWatch, Datadog, Grafana, Prometheus, OpenTelemetry, or ELK
• Solid backend competency in Java (Spring Boot), Python, or Node. Understanding of JVM, concurrency, async systems
• Comfort being the senior infrastructure person. Self-directed, opinionated, disciplined about documentation
• B2/C1 Level English

Nice to have

• Fintech or other regulated industry experience
• DynamoDB at scale (we run many tables with PITR and S3 exports, Lambda-driven daily incrementals)
• AWS cost optimisation track record
• Past experience as a first infrastructure hire at a small team
• Building internal developer platforms or self-service tooling
• AWS DevOps Pro, Solutions Architect Pro, or CKA
• Service mesh experience (Istio, Linkerd) and DevSecOps practices
• Firebase or GCP exposure (we have a small footprint there)

What you won't get from us

• A platform team to lean on. You'll be building that capability
• Click-ops everywhere. You'll be replacing what exists with IaC
• Ambiguity about the work. We know exactly what we need

Working setup

• UK working hours.
• Fully remote across the EU
• Tooling: Microsoft 365, Teams, Planner, Nuclino, GitHub
• aws-vault with MFA enforcement on all accounts
• Sustainable on-call rotation