41. Ad Click Aggregator: Low-Level Design

The brief

Ad Click Aggregator: Low-Level Design. The classes and code behind the ad click aggregator: signed click tokens, a redirect that never waits on the log, and a stream counter that de-duplicates and handles late clicks. Tests run all of it. Work from the scoping questions below. State assumptions for any unspecified load, guarantee or target, then trace your design end to end. Explain one difficult case and a credible alternative; the worked example is a reference, not a required implementation.

• Set the scope: What fields identify an ad click, and which fields may change? How are repeated, late and out-of-order clicks interpreted?
• Define the contract: Which aggregation windows and advertiser queries are required? How do ingestion, aggregation and persistence interfaces report failure?
• Test the boundaries: How would you test recovery between updating a total and acknowledging input?

Constraints

Explicit scope and guarantees

Resolve the scoping questions for Ad Click Aggregator: Low-Level Design. Separate stated behavior from assumptions, and identify what is outside your design.

Supported operating targets

Declare relevant volume, latency, freshness, quality or cost targets with units. Show calculations or an evaluation plan that can test them; unspecified targets are your assumptions, not hidden pass criteria.

Failure and boundary behavior

Explain how your guarantees hold in a difficult case relevant to this subject. Address: How do ingestion, aggregation and persistence interfaces report failure? How would you test recovery between updating a total and acknowledging input?

What to cover

1. 01

   Scope and behavior contract

   Identify users, required behavior and exclusions. Answer: What fields identify an ad click, and which fields may change? How are repeated, late and out-of-order clicks interpreted?

2. 02

   State and interfaces

   Define the information owned by the system and the inputs, outputs and errors at its boundaries. Resolve: Which aggregation windows and advertiser queries are required? How do ingestion, aggregation and persistence interfaces report failure?

3. 03

   Capacity and operating targets

   Estimate the dominant workload and resource demand with units and explicit assumptions. For a learned system, also state how quality is measured and what data is available.

4. 04

   Architecture and central flow

   Draw or describe the responsibilities needed for Ad Click Aggregator: Low-Level Design. Trace a representative request, event or job from its input to a visible result; identify durable state owners.

5. 05

   Failure and boundary walkthrough

   Walk through a difficult case step by step, including detection and recovery. Consider: How would you test recovery between updating a total and acknowledging input?

6. 06

   Tradeoffs and operations

   Compare a credible alternative using your chosen workload and guarantees. Explain a remaining risk, a signal to watch and when you would change the design.

Worked designs

Explore the architecture and decisions, then build on an example with Coach.

Official design

Ad Click Aggregator: Low-Level Design

The classes and code behind the ad click aggregator: signed click tokens, a redirect that never waits on the log, and a stream counter that de-duplicates and handles late clicks. Tests run all of it.

Explore the design

Review rubric

AI feedback uses these criteria. Scores are practice feedback.