Top 21
Prep plan
Updated weekly · Last refresh Aug 30

Reddit Data Engineer Interview Questions

The questions to prepare for a Reddit Data Engineer interview. Questions from real interview reports rank first. Updated weekly.

21questions
~4htotal time
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1
CodingStart here. 7 questions · ~77 min
Client-Side API Rate LimiterMedium
Practice

Use a queue to enforce a sliding-window client-side API rate limiter over request timestamps.

network requestsloopscachingReddit
Maximum Sum Contiguous SubarrayEasy
Practice

Use Kadane's algorithm to find the contiguous subarray with the largest sum in linear time.

Dynamic ProgrammingArraysGreedyReddit
O(1) Insert Delete Random SetEasy
Practice

Implement a set-like structure using an array and hash map to support insert, delete, and random access in average O(1) time.

Hash TablesArraysData StructuresReddit
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2
SQL & Data Manipulation4 questions + 2 drills · ~64 min
3
Pipelines4 questions · ~44 min
Late-Arriving Data in Spark AirflowHard

Tests strategies for correctness and idempotency with late data in batch pipelines.

Batch ProcessingOrchestrationBackfillingReddit
Kafka Streaming DeduplicationHard

Tests deduplication approaches for streaming systems with ordering and idempotency concerns.

Data QualitydeduplicationStream ProcessingReddit
Real-Time Live View PipelineHard

Tests end-to-end streaming pipeline design for low-latency analytics and serving.

Stream ProcessingmonitoringETLReddit
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4
Behavioral & Leadership6 questions · ~66 min
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The finish line: interview-readyComplete all 21 questions plus 2 hands-on drills to finish this plan.