QA Tester - **Must have Active SC Clearance** in London

You will be testing Kafka-based streaming data pipelines at genuinely enormous scale, and you will be writing the test strategy for the whole programme from a blank page. There is nothing in place today.

Our client is a UK-headquartered AI company building sovereign AI capability for defence and national security. They have been established for around a decade and are one of the country's leading builders of AI for high-risk, high-assurance environments. Their platform is an AI operating system built entirely in the UK, designed for settings where security, trust and full infrastructure control are non-negotiable. It deploys across cloud, edge, on-premise and fully air-gapped systems, and is already live inside UK Defence and national security missions.

The client is standing up a new twelve-person team across two work streams, delivering a major UK defence programme through a larger prime contractor. The team is being built from scratch, and this role sits in it from day one. One of those work streams is a data management system ingesting enormous volumes of highly varied data: IoT sensors in the water, weather feeds, transponder data from ships. Streaming, continuous, and at a scale where millions to potentially billions of rows a day is the normal operating picture, not the stress test.

WHAT YOU WILL ACTUALLY DO:

• Test the pipeline, not the page. Own quality across large-scale Kafka streaming and batch data pipelines: ingestion, transformation, reconciliation and output.
• Build the test harnesses. Work directly alongside the data engineers to design and build the harnesses that make this system testable at scale.
• Prove correctness, completeness and integrity across volumes where sampling and eyeballing stop working and you need a genuine strategy.
• Design and build the automated regression suite that runs on every release and proves accuracy, stability and response times have not moved.
• Write the test strategy for this programme. There is a blank page here and the client wants someone who has an opinion about what goes on it.
• Prepare and complete formal test documentation for defence factory assurance: what was tested, how, against which criteria, signed off at each milestone.

This is a small, multidisciplinary team in a scaling business. Everyone gets hands on, including the engineering leadership.

THE FOUR THINGS THAT DECIDE THIS ROLE:

• Hands-on Kafka. Topics, partitions, consumer groups, offsets, replay, schema registry.
• Testing high-volume ETL or ELT data pipelines. Millions of rows a day and upward, in a system real users depended on.
• Writing the test strategy. There is nothing in place on this programme yet.
• Modern architecture. REST, contract testing, schema validation.

ALSO REQUIRED:

• Automated regression testing in CI: repeatable suites that run on every release and check accuracy, stability and response times.
• Comfort working close to data engineers, in the pipeline itself rather than at the UI layer.
• Python and SQL, and a structured, evidence-led approach: defined criteria, traceability, and the discipline to document what you did and why.
• Someone who can operate in a small team where the boundaries are loose and the standard is high.
• SC clearance, or genuine eligibility for it. Active clearance is strongly preferred on contract.

WHAT THE TECHNICAL INTERVIEW WILL PROBE:

• How you tested a pipeline, not just that you did.
• Which technologies, how you handled schema and schema changes, and how you proved it held at volume.
• What runs in your CI when a release goes in.
• How you would build the test strategy here.