Design an Ad Impression Reconciliation and Aggregation Service
Company: Microsoft
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Technical Screen
Overview: Design microservices that reconcile unreliable impression records against an authoritative event source and publish advertiser aggregates. Cover deduplication, late corrections, idempotent reprocessing, audit history, time-bucket summaries, and safe recovery from worker retries.