Python Coding Practice for Data Engineers

Every solution is executed against its tests by scripts/build.py. Run them yourself in the browser with the web platform (Pyodide), or locally: copy the starter, implement, paste the tests.

Read first: The data engineering coding round · Algorithm patterns · Classic DSA problems by pattern: Algorithms track

Easy

#	Problem	Topics
01	Top-K Most Frequent Search Terms	hash-map, heap, counting
02	Flatten Nested JSON Records	recursion, json, schema
03	Deduplicate Records Keeping the Latest Version	hash-map, deduplication, cdc
04	Parse Web Server Logs into Hourly Status Counts	parsing, regex, aggregation
05	Merge Two Sorted Event Streams Lazily	generators, two-pointers, streaming
06	Implement GROUP BY with Multiple Aggregates	hash-map, aggregation, one-pass
07	Validate Records Against a Schema	validation, data-quality, schema
22	Batch a Stream into Fixed-Size Chunks	generators, itertools, streaming

Medium

#	Problem	Topics
08	Merge Overlapping Time Intervals	intervals, sorting, sweep
09	Peak Concurrent Sessions (Meeting Rooms II)	intervals, heap, sweep-line
10	K-Way Merge of Sorted Partition Files	heap, merge, streaming
11	Sessionize User Events	sliding-window, grouping, sessionization
12	Moving Average from a Data Stream	sliding-window, deque, design
13	LRU Cache for Dimension Lookups	design, hash-map, linked-list
14	Point-in-Time Lookup (As-Of Join)	binary-search, as-of-join, versioning
15	Order Pipeline Tasks in a DAG (Topological Sort)	graphs, topological-sort, orchestration
16	Sliding-Window Rate Limiter for an Ingestion API	sliding-window, deque, design
17	Longest Streak of Consecutive Days (O(n))	hash-set, streaks, arrays
18	Count Time Windows with Exact Revenue Target	prefix-sum, hash-map, arrays
19	Running Median of a Latency Stream	heap, streaming, percentiles
20	Infer a Schema from JSON Records	schema, json, type-system
21	Apply a Daily Snapshot to an SCD Type 2 Dimension	scd2, data-modeling, merge
23	Retry Decorator with Exponential Backoff and Jitter	decorators, reliability, error-handling
28	Metrics Decorator: Count Calls, Failures and Latency	decorators, closures, observability
29	Config-Driven Connector Framework (ABC + Registry)	oop, abc, decorators, design
30	Atomic Partition Writer (Context Manager)	context-managers, idempotency, oop
31	Paginated API Reader With Rate Limits (Generator)	generators, pagination, retries
33	Usage Billing With Historical (Effective-Dated) Rates	binary-search, scd2, billing
34	Render Parent/Child Records as an Indented Tree	trees, dfs, hierarchies

Hard

#	Problem	Topics
24	Uniform Sample from a Stream of Unknown Length	sampling, streaming, probability
25	Consistent Hashing Ring for Sharding	hashing, distributed-systems, bisect
26	Bloom Filter for Streaming Deduplication	probabilistic, hashing, deduplication
27	Sort Data Larger Than Memory (External Merge Sort)	external-sort, heap, generators
32	Usage Credit Ledger With Expiring Grants	heap, ledger, design