Question 1

Azure Fabric in Cloud Architecture?

Accepted Answer

**Section 1 — The Context (The 'Why')**
The primary challenge for this design in Cloud/Tools is balancing scale, cost, and reliability. At scale, naive approaches fail: single points of failure cause cascades, schema evolution breaks consumers, and over-provisioning explodes cost. Failure modes include silent data loss from non-idempotent writes, cascading job failures from tight coupling, and operational burden from manual intervention....

Question 2

Azure Functions vs. Logic Apps?

Accepted Answer

Why choose: Different abstraction levels—code vs. workflow. Functions: code-first, serverless; custom logic, APIs, event-driven. Logic Apps: low-code, 400+ connectors; designer-driven. When Functions: complex transforms, code reuse, fine-grained control. When Logic Apps: orchestration with minimal code, SaaS integration, non-devs modifying flows. Scalability: Functions scale with demand; Logic Apps have execution limits (e.g., 90-day run history)....

Question 3

Agile in project management?

Accepted Answer

**Agile**: Iterative development in sprints. Collaboration and adaptability. **Roles**: PO, Scrum Master, team. **Ceremonies**: Planning, standup, review, retro. **Data deliverables**: Pipelines, datasets, quality....

Question 4

Find orders exceeding $1,000 in the last 30 days.

Accepted Answer

**SQL**: WHERE amount > 1000 AND order_date >= CURRENT_DATE - INTERVAL '30 days'. Index on (amount, order_date). Parameterize dates for testing. For streaming: watermark + window agg.

Question 5

Find top 3 products sold based on total quantity.

Accepted Answer

**SQL**: GROUP BY product, SUM(quantity), ORDER BY total DESC LIMIT 3. Or RANK() OVER (ORDER BY SUM(quantity) DESC) with filter rk <= 3. RANK handles ties (same rank); DENSE_RANK for consecutive ranks.

Question 6

List customers with more than 5 orders.

Accepted Answer

**Why HAVING vs WHERE:** WHERE filters before aggregation; HAVING after. For 'more than 5 orders,' you must aggregate first—HAVING is correct. Using WHERE with a subquery is an alternative but less clear.

**Scalability:** (1) Index customer_id, order_id—enables index-only scan for COUNT. (2) For billions of rows: pre-aggregate in a summary table (customer_order_counts) refreshed incrementally....

Question 7

Python list operations.

Accepted Answer

**Core Operations:** Indexing, slicing (lst[i:j:k]), append, extend, insert, remove, pop, sort, reverse. Membership (in) is O(n); for repeated lookup use set.

**Gotchas:** lst.reverse() and lst.sort() mutate in-place, return None. reversed(lst) and sorted(lst) return new iterable/list. lst += [1] mutates; lst = lst + [1] creates new. Slice assignment lst[1:3] = [a,b] can change length.

**Production:** Prefer list comprehensions over manual loops. Use bisect for sorted lists....

Question 8

Unix scripting in data engineering?

Accepted Answer

**Why Unix in Data Eng:** File staging, cleanup, lightweight transforms before Spark. find, awk, sed, xargs, cron—ubiquitous, no runtime deps.

**Use Cases:** find /data -name '*.csv' -mtime +7 | xargs gzip. awk -F',' '{print $1,$3}' for column extraction. sed for bulk replace. Cron for scheduling: 0 2 * * * /scripts/ingest.sh.

**Scalability:** Shell for single-node, pre-processing. For distributed: Spark. Best practice: set -e (exit on error), validate paths, log to file....

Question 9

Convert row-level records to column records.

Accepted Answer

**Architectural Logic**: Pivoting (rows→columns) is a reshape operation with cardinality and performance implications. **SQL**: Aggregate + CASE: `SELECT product_id, MAX(CASE WHEN month='Jan' THEN sales END) AS jan_sales, ... FROM sales GROUP BY product_id`. Or PIVOT (SQL Server). **Spark**: `df.groupBy("product_id").pivot("month").agg(sum("sales"))`. **Why Cardinality Matters**: High cardinality in pivot column (e.g., pivot by user_id) causes column explosion—hundreds of columns, schema bloat....

Question 10

ER Modeling vs. Dimensional Modeling?

Accepted Answer

**Architectural Logic**: ER and dimensional serve different purposes—transactional integrity vs analytical performance. **ER**: Normalized; entities and relationships; OLTP; minimizes redundancy; supports transactional integrity. Many tables; complex joins. **Dimensional**: Star/snowflake; facts and dimensions; OLAP; optimized for analytics. Denormalized; fewer joins; intuitive for business. **Why Both**: ER for operational systems; dimensional for warehouses....

Comcast Data Engineer Interview Questions

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Comcast Data Engineer Interview Questions

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