SQL-Engineering-Handbook

Scoring Rubric

The Eight Competency Dimensions

Score each independently 1-5 — a candidate is rarely uniform across all eight.

Score	Label	Description
1	Beginner	Cannot produce a working answer without significant help
2	Developing	Partially correct; needs guidance to find gaps
3	Competent	Correct independently; explanation is surface-level
4	Strong	Correct + clear mechanism explanation + aware of an edge case/tradeoff unprompted
5	Senior	Correct + mechanism + tradeoffs unprompted + anticipates the follow-up before it’s asked

The Eight Dimensions

1. SQL Correctness — right result including edge cases (NULLs, empty sets, ties)
2. Reasoning — explains WHY, not just recites
3. Data Understanding — reasons correctly about nullability, cardinality, skew
4. Edge-Case Awareness — proactively considers NULLs, ties, duplicates, date/timezone boundaries
5. Performance Awareness — considers cost at scale
6. Maintainability — would another engineer understand and safely modify this
7. Communication — explains approach clearly in real time
8. Production Judgment — investigates before proposing a fix; considers blast radius

Applying It

Not every question exercises every dimension. Score only what’s actually observable; leave the rest blank.

Aggregating

Don’t average blindly into one number — a candidate strong on correctness but weak on communication is different signal than the reverse, and roles weight these differently. Record per-dimension, let the hiring decision weight by actual role needs.

Calibration Across Interviewers

Periodically compare scores on a shared reference question to catch rubric drift between interviewers early.

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