Use the linked documentation to check technical details. Your practical exercise: Clean and aggregate a messy event table, make keys and grain explicit, prevent silent alignment bugs, and validate results against invariants.
The plan
Work through it in order
- 01
Map the official surface
Build a one-page map around indexing, alignment, and missing data, grouping, joins, and reshaping, time series, performance, and testable transformations. For each area, record the contract, the mechanism underneath it, and one production consequence.
- 02
Prepare answer ladders
Practice a 20-second definition, a two-minute explanation with an example, and a deeper trade-off discussion. This keeps answers useful when the interviewer changes depth.
- 03
Solve a realistic scenario
Clean and aggregate a messy event table, make keys and grain explicit, prevent silent alignment bugs, and validate results against invariants.
- 04
Run a closed-book mock
Answer aloud without notes, draw or code the critical path, test a boundary, and check every factual claim against the primary source after the attempt.
Avoidable failure modes
Common mistakes
- Memorizing indexing, alignment, and missing data terminology without explaining behavior
- Ignoring the failure modes and trade-offs around grouping, joins, and reshaping
- Reading summaries repeatedly instead of retrieving and applying the material
Before you move on
Readiness checklist
- indexing, alignment, and missing data explained from first principles
- grouping, joins, and reshaping connected to a production decision
- time series, performance, and testable transformations tested with a concrete boundary
- One timed mock reviewed against official documentation
Quick answers
Frequently asked questions
Which topics should I cover?
Start with indexing, alignment, and missing data, grouping, joins, and reshaping, time series, performance, and testable transformations. Confirm the exact role and interview format with the recruiter, then deepen the areas emphasized in the job description.
How should I use this preparation plan?
Clean and aggregate a messy event table, make keys and grain explicit, prevent silent alignment bugs, and validate results against invariants. Explain decisions aloud, test an edge case, then check the result against the linked documentation. Repeat the exercise with one changed constraint after feedback.
Source notes
References and review policy
Source links provide further reading. Where a recorded technical review is available, the answer shows its date and scope. Tool selections use direct provider links and contain no affiliate placements. Sources, features, and hiring formats can change.
From reading to recall
Practice the full interview loop.
RecallDeck schedules the concepts you miss and keeps coding, design, and behavioral fundamentals available when the interviewer changes direction.