Question 1

Amazon Deequ usage and what sort of quality checks are done using it?

Accepted Answer

**Deequ**—AWS data quality library. **Checks:** Completeness (non-null), uniqueness, consistency (constraints), statistics. **Example:** customer_id unique; age 0–120. **Output:** CloudWatch metrics. **Glue:** Profiling integration. **Why:** Code-defined checks; CI integration. **Scalability:** AnomalyDetection for drift. **Cost:** Minimal—runs with Glue....

Question 2

Given 1TB of a file, how to check word count?

Accepted Answer

**Distributed:** Spark: `textFile().flatMap(split).map(w=>(w,1)).reduceByKey(add)`. Or Hadoop MapReduce. **Single:** Stream chunks. **Why:** Won't fit memory. **Scalability:** Partition by file/split. **Production:** Spark for 1TB.

Question 3

Shell: how to run jobs/scripts in the background?

Accepted Answer

**Why Background Jobs:** Long-running ETL, API polling—don't block terminal. nohup ensures survival after logout (SIGHUP ignored).

**Mechanics:** & backgrounds; nohup cmd > out.log 2>&1 & persists. jobs, fg, bg, kill for management. disown detaches from shell. screen/tmux for multiple sessions.

**Production:** Always redirect stdout/stderr. Cron uses nohup for scripts that might outlive the cron process....

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Citi Python Interview Questions

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