3. How Does Your API Work?

Question 1

What are the two parts that every HTTP request and response have?

Answer 1

The headers and the payload.

Question 2

What is a HTTP request or response’s payload?

Answer 2

HTML, JSON, XML…

Question 3

What range of HTTP response codes indicate that the request was successful?

Answer 3

2xx

Question 4

What does the 2xx HTTP response code series indicate?

Answer 4

That the request was successful.

Question 5

What does the HTTP response code 200 mean?

Answer 5

It simply means “OK.”

Question 6

What does the HTTP response code 201 mean?

Answer 6

It means “Created.”

Question 7

What does the HTTP response code 202 mean and what is it used for?

Answer 7

It means “Accepted.” It’s used for identifying that the action the user just performed is underway, but it’s not complete yet.

Question 8

What does the HTTP response code 204 mean, and when is it primarily used?

Answer 8

It means “No Content.” It’s primarily used when deleting a resource.

Question 9

What does the 3xx HTTP response code series indicate?

Answer 9

That the resource has been moved from its original URL.

Question 10

What does the HTTP response code 301 mean?

Answer 10

It means “Moved Permanently” as in what you’re looking for is no longer available here. Most responsible APIs will then give you the URL to then retrieve it.

Question 11

What does the HTTP response code 302 mean?

Answer 11

It means “Moved Temporarily.”

Question 12

What does the 4xx HTTP response code series indicate?

Answer 12

That a client error has occurred.

Question 13

What does the HTTP response code 400 mean and what does it indicate?

Answer 13

It means “Bad Request,” denoting that the most recent attempt failed due to the client itself.

Question 14

What does the HTTP response code 401 mean and what does it indicate?

Answer 14

It means “Unauthorized,” which indicates that the required authentication credentials were not provided or the authentication has failed.

Question 15

What does the HTTP response code 403 mean and what does it indicate?

Answer 15

It means “Forbidden,” which indicates that the user making the request is not authorized to access the API point that’s being requested.

Question 16

What does the HTTP response code 403 mean and what does it indicate?

Answer 16

It means “Not Found,” which indicates that the resource you’re looking for does not exist.

Question 17

What does the Content-Type HTTP header identify?

Answer 17

The type of the payload being provided by the server.

Question 18

Are you required to follow the six constraints of RESTful API?

Answer 18

No. They are not hard and fast requirements but are good design principles you should follow.

Question 19

What are the six architectural constraints of RESTful API?

Answer 19

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 20

What is stateless architecture and what does it allow for each request?

Answer 20

It’s an architectural constraint of RESTful API that states that the API should be stateless. This allows each and every request to stand on its own and be processed or rejected independently of any other request in any order that they’re received.

Question 21

What is client-server architecture and what is its biggest benefit?

Answer 21

It’s an architectural constraint of RESTful API that states that the API should be designed for a client-server architecture. The biggest benefit of this is that it allows us to vary the implementation details, upgrade paths, and scalability of each independently of the other.

Question 22

What are the characteristics/benefits of a stateless architecture for HTTP requests/responses.

Answer 22

1. Inherent to the design of the internet
2. Stability
3. Scalability
4. Reliability
5. Flexibility

Question 23

What is cacheability mean in the context of RESTful API architecture and what does it require?

Answer 23

It’s an architectural constraint of RESTful API that deals with whether a response pair can be cached. It requires that each message describes whether it can be cached and if so, for how long.

Question 24

What is the benefit of cacheability?

Answer 24

It allows the API to know when it’s possible to just return the result, instead of doing the work. This improves network performance and application usage overall.

Question 25

What does idempotency mean in the context of cacheable API requests?

Answer 25

It means that whether we execute the command 1 or N+1 times, the state of the server is exactly the same.

Question 26

What HTTP requests should we strive to make idempotent, and what ones are tricky in regards to this?

Answer 26

1. GET, PUT, and DELETE can and should be idempotent.

2. POST is tricky. Since it can create or change the state, sometimes it’s idempotent but oftentimes it’s not.

Question 27

What do layered systems mean in the context of RESTful API architecture?

Answer 27

It means that a given component might or might not communicate with another component and that your client should not be built with the assumption that it’s communicating directly with the server. There can and often will be additional layers between the client and the server itself.

Question 28

What are the characteristics of layered systems?

Answer 28

1. They are how the web is built
2. Counting on direct connections/interactions adds silent, hidden dependencies, which is not the case with layered systems
3. Allow us to add DNS lookups, load balancers, caching servers, logging, audit trails, authentication, and authorization
4. Layers give us flexibility to improve and evolve our system as our requirements and the architecture changes.

Question 29

What is “Code on Demand” in the context of RESTful API architecture?

Answer 29

It means that a request doesn’t just retrieve a resource, but also the code to act upon it and that the client doesn’t have to know what is in the code, it just has to understand how to execute the code.

Question 30

What are the benefits of Code on Demand?

Answer 30

1. Flexibility
2. Upgradability
3. Extensibility

Question 31

What are the six architectural constraints of RESTful API?

Answer 31

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 32

What are the six architectural constraints of RESTful API?

Answer 32

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 33

What are the six architectural constraints of RESTful API?

Answer 33

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 34

What are the six architectural constraints of RESTful API?

Answer 34

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 35

What are the six architectural constraints of RESTful API?

Answer 35

1. Client-Server Architecture
2. Stateless Architecture
3. Cacheability
4. Idempotency
5. Code on Demand
6. Uniform Interfaces

Question 36

What are the four principles that make up a uniform interface?

Answer 36

1. Identification of resources.
2. Manipulation of resources through these representations.
3. Self-descriptive messages.
4. Hypermedia as the engine of application state (HATEOAS)

Question 37

What does the “identification of resources” dictate in the context of designing uniform interfaces?

Answer 37

each resource should be uniquely addressable by a particular URL (though not a hard and fast requirement).

Question 38

What does “manipulation of resources through these representations” dictate in the context of designing uniform interfaces?

Answer 38

That every interaction with a given resource should happen through the identifier (endpoint) that we already gave it.

Question 39

What does “self-descriptive messages” dictate in the context of designing uniform interfaces?

Answer 39

That the messages should be standalone with their own processing and caching information, allowing us to create and use different types of messages very simply. This means that our client only needs to know how to retrieve and execute those instructions like the JavaScript code on demand that we see on the internet.

Question 40

What does “hypermedia as the engine of application state” dictate in the context of designing uniform interfaces?

Answer 40

HATEOAS dictates that instead of users having to go to the documentation for what’s available, each and every link must be provided to them through the API (think choose-your-own-adventure books).

Question 41

What is the biggest benefit of hypermedia as the engine of application state?

Answer 41

HATEOAS allow our apps to discover links. In effect, our apps don’t have to know every link in advance. Instead, they must know only how to discover them.