About

Senior offers come from interview rounds that LeetCode skips: code review, debugging, system design. Senior Loop trains those.

Senior Loop was built because every senior backend engineer we know had been through interview rounds that no prep tool covered honestly. LeetCode prepped the phone screen; nothing prepped the loop after. So we built it.

Each PR is hand-authored from a real production pattern. The grader uses Claude Sonnet 4.5 against a hand-authored bug list — not a generic LLM inventing feedback. Your score reflects what was planted.

The catalog spans 15 PRs across payments, distributed systems, security, API design, observability, performance, and ops. More shipping regularly, based on what real reviewers catch and miss.

How it works

Each PR in the catalog is hand-crafted from a real production pattern. Bugs are planted with hand-authored metadata — severity, category, and a rubric. When a review is submitted, an AI grader (Anthropic Claude Sonnet 4.5) compares the candidate's inline comments to the ground-truth bug list and scores against a senior-engineer rubric.

The grade reflects what was planted, not what a generic LLM happens to invent that day. False positives are penalized; comment quality matters as much as catching bugs.

What's live today

• Code Review: 15 PRs across payments, distributed systems, security, API design, observability, performance, and ops.
• Debugging: 10 broken-codebase exercises with failing tests and log excerpts. Payments, distributed systems, concurrency, security, performance, observability, api, ops.
• System Design: on the roadmap.

Languages

The catalog is available in Go, Kotlin, Python, Java, and C#. Reviewers pick the language they think in; the same PR and rubric translate across all five.

Pricing model

Three free PRs, no card required. Paid plans (Monthly / Annual) unlock the full catalog. No auto-renewal — access ends when the period expires; the catalog re-locks until the next manual purchase. See the Pricing page for current rates.