The Event Pile

A hard Pipeline Design interview practice problem on DataDriven. Write and execute real pipeline design code with instant feedback.

Domain

Pipeline Design

Difficulty

hard

Seniority

L7

Problem

We run a product that emits hundreds of millions of user interaction events a day into Kafka, and right now they just pile up with no good way to query them. Three groups depend on this data: analysts run funnel studies that scan months of events by type, customer support has to pull up a single user's full session while the customer is still on the phone, and product teams watch dashboards that aggregate the last hour. Every event has to stay queryable for two years and the storage bill is already too high, so design an architecture that serves all three access patterns without keeping the whole history on expensive always-on storage.

Summary

600 million clicks a day. The budget is not infinite.

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