Interview · ClickHouse
Backend / C++ Engineer at ClickHouse: what they ask
High-performance open-source columnar analytics database.
Aggregated from public reports (2026). Add yours to keep it fresh.
The process
- Recruiter screen (~30m): motivation, experience, an initial CV deep-dive.
- Technical phone (~60m): C++ + data structures/algorithms.
- Onsite loop (~5 rounds): 2 coding (often low-level, performance), 1 system design (database internals), 1 deep-dive on a recent project, 1 behavioral.
- Often a substantial take-home. Total cycle ~3-5 weeks.
What they ask
- C++ coding with a performance focus (cache, allocations, hot path).
- System design centered on database internals (storage, query execution, concurrency).
- Deep-dive: walk through a recent project — tradeoffs, scope, impact.
- Behavioral: collaboration, end-to-end ownership.
How they behave
Less "interview theater", more: can you own a real problem end to end? Conversations are described as friendly and CV-driven; they reward explaining tradeoffs and impact, not reciting architectures. Very much for people who genuinely care about cache lines, SIMD and microseconds.
How to prepare
- Modern C++ + data structures, with a performance focus (profiling, memory).
- Columnar / OLAP database internals; read how ClickHouse itself works.
- Prepare 1 project to tell in depth: problem, choices, tradeoffs, outcome.
Full intel + fresh reports
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