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A themed six-round mock interview simulating a real Netflix Data Engineer loop. Covers SQL analytics on viewing behavior, data pipeline architecture for streaming events, dimensional modeling for the content catalog, behavioral questions around Netflix's Freedom & Responsibility culture, and a Python DSA problem built around recommendation data structures.

Netflix Data Engineer Interview

Netflix tracks every viewing session in a table called `viewing_sessions`:

viewing_sessions (
    session_id BIGINT PRIMARY KEY,
    user_id BIGINT,
    title_id BIGINT,
    country_code VARCHAR(2),
    genre VARCHAR(50),
    watch_duration_minutes INT,
    started_at TIMESTAMP
  )

Write a SQL query that returns the top 3 most-watched genres (by total watch minutes) per country for the last 30 days. Include: country_code, genre, total_watch_minutes, and rank_within_country.

Handle ties by including all genres that tie for 3rd place.

**Expected strong answer includes:** Window function (DENSE_RANK or RANK partitioned by country_code), date filter using started_at, clear CTE structure, correct tie-handling semantics.

Top 3 Most-Watched Genres per Country — Netflix

Using the same viewing_sessions table, a "binge streak" is defined as 3 or more consecutive days where a user watched at least 2 hours total.

Write a SQL query that returns each user's longest binge streak in the last 90 days: user_id, streak_start_date, streak_end_date, streak_days, total_minutes_watched_during_streak.

Output should be one row per user (their longest streak only). Users with no qualifying streak should not appear.

**Expected strong answer includes:** Gaps-and-islands technique, daily aggregation CTE, consecutive-day grouping using ROW_NUMBER difference trick, proper date arithmetic.

Detecting Binge-Watch Streaks — Netflix

Star schema with clear fact_viewing_sessions at session grain, conformed dimensions (dim_title, dim_date, dim_user, dim_device, dim_geography), SCD2 tracking columns (valid_from/valid_to), bridge table for multi-valued genres, clear grain statement.

Netflix Content Catalog Dimensional Model

Kafka/Kinesis for ingestion, schema registry for evolution, Flink/Spark Structured Streaming for enrichment, Lambda/Kappa architecture considerations, S3 + Iceberg for the batch layer, a fast OLAP store (Druid/Pinot/ClickHouse) for real-time dashboards, dead-letter queues for late arrivals, idempotent replay strategy for backfill.

Real-Time Viewing Event Pipeline — Netflix

Specific technical scenario (not vague), evidence of direct communication, shows intellectual humility, demonstrates the Netflix value of "disagree then commit," acknowledges trade-offs.

Netflix Culture: Radical Candor Conflict

Concrete system (not abstract), demonstrates initiative (they drove it, not assigned), shows awareness of why complexity accumulated (not blame), evidence of stakeholder management, quantified improvement (latency, incidents reduced, onboarding time), demonstrates the Netflix principle of "highly aligned, loosely coupled.

Netflix Culture: Simplifying a Complex System

Netflix's trending algorithm needs to detect titles whose hourly view count 
exceeds 2x their trailing 24-hour average at any point.

You are given a stream of events as a list of tuples:
  events: List[Tuple[int, str]]  # (unix_timestamp, title_id)

Implement:

def find_trending_titles(events: List[Tuple[int, str]], window_hours: int = 24, spike_multiplier: float = 2.0) -> List[Tuple[str, int]]:
    
Returns a list of (title_id, spike_timestamp) for every title that spiked above spike_multiplier * its trailing window_hours average  at any hourly boundary.
    
Events are NOT guaranteed to be sorted by timestamp. A title can appear multiple times if it spikes more than once.
    

Constraints:
- Events list can contain up to 10 million entries
- Timestamps span up to 30 days
- Optimize for O(n log n) or better
- Use only standard library (collections, heapq, bisect allowed)

Sliding Window: Trending Titles Detector — Netflix

Modified Dijkstra's algorithm with genre-filtering at node expansion, correct distance = 1 - similarity transformation, heap-based priority queue, handles disconnected graph, O((V + E) log V) complexity.

Netflix Data Engineer Interview

In order. Round N+1 unlocks when Round N passes.