Design
Ad Click Tracking & Billing System
Design a system that tracks ad impressions/clicks at massive scale and computes accurate billing for advertisers.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
Ad-tech billing tests exactly-once event processing under fraud pressure — interviewers check if you separate a fast real-time layer from a rigorous, fraud-filtered billing layer.
02 - Where this system exists in the real world
You interact with this design every day.
Google Ads / Meta Ads click-tracking infrastructure
Affiliate marketing attribution systems
Programmatic ad exchange billing pipelines
03 - What you'll master
Solve this once. Know it forever.
Design a durable, high-throughput event ingestion path
Separate real-time metrics from authoritative billing
Apply fraud-detection heuristics before billing
04 - What you'll design
6 functional · 3 non-functional requirements.
Record ad impressions and clicks with low latency
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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