just finished my BCG DE loop last month, posting while it's fresh. applied to their Advanced Analytics Engineering team, not a pure tech product team, so keep that context in mind.
Five stages in total. Recruiter screen was quick, 25 minutes. She described the role as building and maintaining data infrastructure for consulting engagements. translation: your pipelines feed client deliverables, not a product.
Round 1: technical SQL screen (60 min) Two exercises. First was a complex aggregation problem: compute rolling 30-day active users segmented by region and business unit, given a messy events table with nulls and duplicates. The second was more conceptual: design a SQL query to detect outliers in transaction amounts per merchant. They pushed on indexing, how I'd handle the performance at scale, and whether I'd use window functions or subqueries (I went window functions, they seemed satisfied).
Round 2: pipeline design (45 min) No specific tool required. They gave me a scenario: a client wants daily reports on supply chain metrics, data comes from 3 source systems with different schemas and refresh cycles. Walk us through how you'd design the ingestion and transformation layer. I talked through orchestration (Airflow, briefly Dagster), idempotency, failure handling, schema evolution. They asked specifically about how I'd handle late-arriving data.
Round 3: mini case Yeah, data engineers get the case too. Mine was lighter than what consultants get but it still required me to structure a data problem for a hypothetical retail client. What metrics would you prioritize? How would you present findings to the CEO? I was not expecting this and I stumbled a bit. Practice this.
Round 4: behavioral + culture Two interviewers, 75 minutes. Behavioral was classic: a time you disagreed with a technical decision, a time you had to deliver bad news about a data quality issue, cross-functional collaboration under pressure. They care a lot about how you communicate with non-technical folks.
I got a verbal offer, waiting on written. TC for senior DE in a major metro is apparently in the $165-185k range all-in based on what the recruiter mentioned, but I'll know more when the packet comes.