Design a key-value cache to save the results of the most recent web server queries

Step 1: Outline use cases and constraints

Use cases

We'll scope the problem to handle only the following use cases

Constraints and assumptions

State assumptions

Calculate usage

Step 2: Create a high level design

Step 3: Design core components

Use case: User sends a request resulting in a cache hit

Cache implementation

When to update the cache

Step 4: Scale the design

Expanding the Memory Cache to many machines

Additional talking points

SQL scaling patterns

NoSQL

Caching

Asynchronism and microservices

Communications

Security

Latency numbers

Ongoing