769 posts: company guides, SQL and Python walkthroughs, system design, A/B testing, career advice.
Mean Absolute Error in SQL with a runnable template, MAE vs RMSE comparison, bias decomposition, per-segment drill, weighted variant, drift monitoring, and FAQ.
Read →Mean Average Precision@k in SQL: per-query average precision, mean across queries, MAP vs MRR vs NDCG, pitfalls, and FAQ for recsys analysts.
Read →How dbt tests work in real pipelines: generic, singular, custom macros, severity thresholds, store_failures, plus interview pitfalls to avoid.
Read →A/B testing for beginners: the experiment loop, the vocabulary, the math you actually use, and the five mistakes that kill most first-time tests.
Read →AARRR pirate metrics walkthrough: Acquisition, Activation, Retention, Revenue, Referral. SQL examples, dashboard layout, interview answers, and common pitfalls.
Read →NPS explained for product managers: the formula, what counts as a good score, sampling rules, and pitfalls that quietly inflate your number for stakeholders.
Read →Lambda functions in Python: syntax, sorted, map, filter, pandas apply. When to reach for lambda, when to use def, and interview gotchas every analyst should know.
Read →Python set explained for analysts: unique values, union, intersection, difference, O(1) lookups, frozenset, and real interview questions with worked code.
Read →Druid for DE interviews: architecture tiers, segments, real-time ingestion, SQL queries, and how it compares to ClickHouse — with worked examples and pitfalls.
Read →Hive on the DE interview: HiveQL, partitioning, bucketing, file formats, execution engines, and how it compares to Spark SQL and Trino in 2026.
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