System designMediumsd-g148

Subject Eta predictionLevel Mid–Senior~40 minCommon in Distributed systems interviewsIndustries Technology

Question

Design the live order-tracking and arrival-prediction service shown to a customer after they place a delivery order: a moving courier marker, a continuously-updated 'arriving in N min' estimate, and a notification when the courier is ~2 minutes away. 2M active tracked orders at peak. Cover how the estimate is computed and refreshed, and how the 'almost there' trigger works without false alarms.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

Loading whiteboard…

Run or narrate your approach, then ask the coach.