Basics

Question 1

What is HTTP?

Answer 1

Hypertext Transfer Protocol. Protocol that defines how messages are formatted and transmitted between web browsers and servers. Human readable.

Question 2

What is HTML?

Answer 2

Hypertext Markup Language. Standard language for creaing web pages. It uses tags to structure content.

Question 3

How does a GET http message look like?

Answer 3

The GET message which specifies the GET method looks like this:

GET /path/to/resource HTTP/1.1
Host: 127.0.0.1:3000
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Question 4

In which layer does HTTP works?

Answer 4

Application layer

Question 5

What does it mean for HTTP to be stateless?

Answer 5

Means that the receiver must not retain a state from previous requests.

Question 6

In which 3 locations can the cache be?

Answer 6

Browser cache, proxy server, reverse proxy server.

Question 7

What is stale content?

Answer 7

Cached content that it’s expired.

Question 8

What is cache validation?

Answer 8

Process of contacting the server to check the validity of cached content.

Question 9

What is cache invalidation?

Answer 9

The process of removing any stale content in the cache.

Question 10

How does content get cached?

Answer 10

Whenever a server sends a response message to the client, it sets some headers that are used by the client or any of the intermediate places to cache the content.

Question 11

Why is the Cache-Control header preferred over others caching headers?

Answer 11

It was introduced with HTTP 1.1 and it is a multivalue header, which means it can return multiple directives of how the caching behavioir should be.

Question 12

What does “Cache-Control: Private” mean?

Answer 12

It means that the content should only be cached in the client.

Question 13

What does “Cache-Control: Public” mean?

Answer 13

It means that the content can be stored in proxies.

Question 14

What does “Cache-Control: no-store” mean?

Answer 14

That the content should never be cached.

Question 15

What does “Cache-Control: no-cache” mean?

Answer 15

The content can be cached but the client must validate the content using the ETag header.

Question 16

What does “Cache-Control: max-age=3600” mean?

Answer 16

That the content is cached for a maximum of 3600 seconds.

Question 17

What does “Cache-Control: max-age=3600, must-revalidate” mean?

Answer 17

It means that after the max age has expired, the client must fetch the content from the server instead of the cache.

Question 18

What are the default ports for HTTP and HTTPS?

Answer 18

80 and 443

Question 19

What an ETag?

Answer 19

Entity Tag. When the server serves content, it usually marks it with an ETag. This ETag is used to check if cached content must be fetched again.

Question 20

What are the 6 things that an HTTP server do?

Answer 20

1. Listens
2. on a port
3. for requests
4. over the TCP
5. returns a response
6. and the resource requested.