Section checkpoint

Foundations

8 questions drawn from the 4 chapters in this section. If most land on the first try, you are ready for the next section. If not, the explanation after each answer says which idea to revisit.

Checkpoint

8 questions · first-try answers earn the most XP

1. What do keep-alive connections and a CDN each remove from page load time?

2. What does the TLS handshake add beyond encryption?

3. What does a health check do for a load balancer?

4. What is the minimum arrangement the chapter calls credible high availability?

5. Why should a rate-limited endpoint return 429 with a `Retry-After` header rather than simply failing?

6. Why should an error body carry both a machine code and a human message?

7. Why are session cookies usually marked httpOnly in production?

8. When does a stateful server-side session actually beat a stateless JWT in a real product?

What this checkpoint covers

DNS, HTTP, TCP in 10 Minutes
What happens when you type a URL.
Load Balancing Intro
Round-robin, least-conn, sticky — why we need it.
API Design Basics
REST, idempotency, pagination, rate limits.
Auth Basics: JWT & OAuth
Sessions vs tokens, OAuth flow, where to validate.

Put it to work in a drill

Sessions and cache share one Redis
Intermediate
Embedded members in an autoscaling app
Intermediate

Next section: Data Layer