Everything Else

Question 1

Four-Layer Web Architecture

Answer 1

Described in Domain Driven Design. Common in OO applications.

• Presentation
• Application
• Business Logic
• Data Access Layer

For mobile apps,

• Client tier (presentation)
• Delivery tier (Cache, Collects user analytics)
• Aggregation tier
• Services tier (3rd party and data stores)

Question 2

Memoization

Answer 2

• Ensures that a method doesn’t run for the same inputs more than once by keeping a record of the results for a given input (typically in a hashmap)

Question 3

Three-Layer Web Architecture

Answer 3

• Presentation
• Domain Logic
• Data Storage

Purists consider “layer” a logical, categorical distinction and tier a physical distinction. So a 3-layer web app could run on a single tier.

Question 4

What happens when you type a URL in your browser?

Answer 4

1. Browser checks cache. If the requested object is in the cache and fresh enough,

Question 5

NP Hard

Answer 5

no polynomial time know solution for this problem