Software Engineer

Software Engineer: Backend & Core Systems

Hollow Sun Industries · Full-time

We build the operational software layer for Europe's most consequential

institutions — defence, energy, healthcare, industry.

THE WORK

You own a domain end to end — ingestion, core application logic, the

service mesh, the storage layer — and you are accountable for its

correctness, latency, cost, and failure modes. Not the story points.

You are involved across the entire product lifecycle: idea, design,

prototype, production delivery, and the three years of operation after.

You will sit with non-technical people who understand the problem better

than you do, and you will translate.

You debug incidents where the stack trace lies and the metrics disagree.

You propose architecture in writing, get taken apart in review, and

either hold your position with evidence or change it without ego.

WHAT WE REQUIRE

- Demonstrated proficiency in at least one systems language — Java, C++,

Rust, Go — plus fluency in Python. Not exposure. Proficiency.

- In-depth command of data structures, system architecture, API design for

microservices, distributed systems, and consensus and consistency

tradeoffs you can defend under questioning.

- Experience designing, shipping, supporting and maintaining live backend

systems. You have carried the pager for something you built.

- Familiarity with storage and data processing systems, database internals,

query planning, and cloud infrastructure. You know why your query is slow

before you open the profiler.

- Performance work with numbers attached. A p99 you moved by an order of

magnitude, and the exact reason it worked.

- Security-conscious engineering. Cloud, on-premise, and air-gapped or

restricted environments are all in scope. Data sensitivity is not

theoretical here.

- Engineering background in Computer Science, Mathematics, Software

Engineering, Physics or similar — or a body of work that makes the

question irrelevant. We check the work, not the credential.

- Exceptional written and verbal communication. You iterate fast, absorb

feedback, and hold an uncomfortably high bar for quality. If you cannot

write, you cannot work here.

DO NOT APPLY IF

You need the problem fully specified before starting.

You measure contribution in output rather than outcome.

You want the codebase to be someone else's responsibility at 2 a.m.

TO APPLY

Send the thing you built that you are proudest of, and one paragraph on

what you would do differently now.