About us

Sleep.ai is an AI-powered sleep platform on a mission to change the world through the power of sleep. We help companies build sleep insights, coaching and research-backed solutions into their products and services, and we power consumer products such as the SleepScore app. We have offices in San Diego, Dublin and Berlin.

We are seeing growing traction and interest, and the number of users joining our platform is climbing quickly. Our platform runs on Azure, using Function Apps, Storage Queues, Blob Storage and Table Storage. We need to understand where it will struggle as load grows, and what needs to change so it can scale.

Learn more: www.sleep.ai

The role

We are looking for an experienced Performance Test Engineer to assess the scalability, stability and responsiveness of our platform under varying load. You will identify bottlenecks, carry out root cause analysis and give us a clear, prioritised plan to resolve them.

You will lead the performance testing effort, working in close collaboration with our backend and DevOps teams to agree priorities, shape the approach and review findings. You will recommend appropriate tooling, with selections reviewed and approved by the engineering team to ensure they fit our platform and existing practices.

Key responsibilities

Define a performance testing strategy and test plans in collaboration with the backend and DevOps teams, covering load, stress, spike, soak/endurance and scalability scenarios
Establish performance baselines and capacity limits for the current platform
Build realistic user-journey and message-volume scenarios and execute them using load testing tools reviewed and approved by the engineering team (for example k6, JMeter, Gatling, Azure Load Testing or similar)
Analyse Function App behaviour: cold starts, scale-out limits, concurrency settings and hosting plan suitability
Analyse queue behaviour: throughput, backlog growth, poison messages, retry patterns and processing lag
Analyse Blob and Table Storage behaviour: throttling, partition design, hot partitions, storage account scalability targets and latency under load
Use observability and monitoring tooling (for example Application Insights, Azure Monitor, Log Analytics or similar) to trace requests, correlate metrics and pinpoint root causes
Produce clear performance reports with findings, risks and prioritised recommendations for both technical and non-technical stakeholders
Recommend fixes and, where agreed, help implement them, then re-test to confirm the improvement
Define SLOs, regression thresholds and quality gates that can be built into our CI/CD pipeline

Essential skills and experience

Proven experience as a Performance Test Engineer or Performance Engineer (typically 5+ years)
Hands-on experience with performance testing tools (for example k6, JMeter, Gatling, NeoLoad or similar)
Strong background in bottleneck analysis and troubleshooting on cloud-hosted distributed systems
Solid working knowledge of Azure serverless and storage services: Functions, Storage Queues, Blob Storage and Table Storage
Experience with APM and observability tooling (for example Application Insights, Azure Monitor, Dynatrace or similar)
Able to script in a language suited to the task (for example C#, JavaScript, Python or similar)
Strong written communication skills, with the initiative to lead the work and the ability to collaborate closely with backend and DevOps teams

Desirable

Experience with cloud-based load testing services and CI/CD pipelines (for example Azure Load Testing, Azure DevOps, GitHub Actions or similar)
Familiarity with messaging and data services that could form part of a future scale-up path (for example Service Bus, Event Hubs, Cosmos DB, Durable Functions or similar)
Previous experience working with startups or scale-ups

Engagement

Type: Contract, part-time

Hours: 10–15 hours per week

Duration: initial term, e.g. 8–12 weeks, with option to extend

Location: remote / hybrid, Ireland-based preferred

Rate: €35 – €50/Hour

Reporting to: Head of Quality Assurance

Expected deliverables

A baseline performance report for the current platform
A bottleneck and risk register, ranked by impact
A scaling roadmap with recommended changes and effort estimates
A reusable load test suite, ready to run in our pipeline

Performance Test Engineer

Job Description