Tutorial: AWS Certified Developer - Associate (DVA-C02)

Common HTTP error codes

Concepts

1. 4xx Client Errors:

These errors occur when the issue stems from the client side.

400 Bad Request: The server cannot process the request due to a client error (e.g., malformed request syntax).
Example: A client sends an HTTP request with a malformed JSON body, the server would respond with a 400 status code.
401 Unauthorized: The request lacks valid authentication credentials for the target resource.
Example: An API request without proper AWS Signature for AWS API Gateway might result in a 401 error.
403 Forbidden: The client does not have access rights to the content; unlike 401, the client’s identity is known to the server.
Example: A user trying to access an S3 bucket without the correct IAM permissions would receive a 403 error.
404 Not Found: The server can’t find the requested resource. In an API, this can also mean that the endpoint is valid but the resource itself does not exist.
Example: Accessing a non-existent Lambda function through API Gateway could lead to a 404 error.
429 Too Many Requests: The user has sent too many requests in a given amount of time (“rate limiting”).
Example: If a client exceeds the API Gateway’s rate limit, a 429 error is returned.

2. 5xx Server Errors:

These indicate problems with the server.

500 Internal Server Error: A generic error message indicating an unexpected condition was encountered by the server.
Example: A Lambda function triggered by API Gateway crashes due to a code exception, causing a 500 error.
502 Bad Gateway: The server, while acting as a gateway or proxy, received an invalid response from an upstream server.
Example: API Gateway could return a 502 error if it receives an invalid response from a back-end service like a Lambda function.
503 Service Unavailable: The server cannot handle the request because it is overloaded or under maintenance.
Example: If an application deployed on Elastic Beanstalk is overwhelmed with traffic, it may return a 503 error.
504 Gateway Timeout: The server, while acting as a gateway or proxy, did not receive a timely response from an upstream server.
Example: API Gateway could return a 504 error if a connected Lambda function times out.

Here is a simple comparison of these common errors:

Status Code	Category	Meaning
400	Client Error	Bad Request due to client’s malformed syntax
401	Client Error	Unauthorized request lacking valid credentials
403	Client Error	Forbidden content cannot be accessed by the client
404	Client Error	Not Found, resource doesn’t exist
429	Client Error	Too Many Requests, rate limiting exceeded
500	Server Error	Internal Server Error, a general error
502	Server Error	Bad Gateway due to invalid response from an upstream server
503	Server Error	Service Unavailable because the server is overwhelmed or down
504	Server Error	Gateway Timeout due to a lack of timely response from upstream

While studying for AWS Certified Developer – Associate, it’s essential to understand how these HTTP statuses can inform you about the behavior of your cloud applications and how you can handle these errors effectively in your code, deployment strategies, and overall architecture choices. They play a vital part in API development, service communication, and troubleshooting. Understanding these codes will aid you in designing resilient and user-friendly applications on AWS.

Answer the Questions in Comment Section

Question 1: Which of the following HTTP status codes represents ‘Not Found’?

1) 404
2) 403
3) 500
4) 502

Answer: A

Explanation: The 404 status code is returned when the requested resource is not found on the server.

Question 2: True or False: The HTTP 500 status code indicates an ‘Internal Server Error’.

1) True
2) False

Answer: A

Explanation: The HTTP 500 status code means there is a generic error and the server cannot identify the specific problem.

Question 3: The HTTP status code 503 signifies what condition?

1) Unauthorized
2) Service Unavailable
3) Bad Request
4) Forbidden

Answer: B

Explanation: The 503 status code indicates that the service is temporarily unavailable, usually due to maintenance or overloading.

Question 4: Which HTTP status code implies that the request was successful?

1) 404
2) 200
3) 302
4) 500

Answer: B

Explanation: The 200 status code is the standard response for a successful HTTP request.

Question 5: Which of the following is a redirect status code?

1) 201
2) 401
3) 301
4) 501

Answer: C

Explanation: 301 status code is used for permanent URL redirection.

Question 6: True or False: An HTTP status code in the range of 4xx indicates a client error.

1) True
2) False

Answer: A

Explanation: Status codes ranging from 4xx indicate client errors where the request contains incorrect syntax or cannot be fulfilled.

Question 7: The HTTP status code for ‘Forbidden’ is:

1) 401
2) 403
3) 404
4) 400

Answer: B

Explanation: 403 status code means that the server understood the request but refuses to authorize it.

Question 8: What status code indicates that a request conflicts with the current state of the server?

1) 409
2) 406
3) 411
4) 402

Answer: A

Explanation: 409 Conflict indicates that the request could not be completed due to a conflict with the current state of the resource.

Question 9: The HTTP status code 202 is known as:

1) Accepted
2) No Content
3) Non-Authoritative Information
4) Reset Content

Answer: A

Explanation: The 202 status code denotes that the request has been accepted for processing, but the processing has not been completed.

Question 10: Which status code should be used when a resource has permanently moved to a new URL?

1) 300
2) 301
3) 410
4) 302

Answer: B

Explanation: 301 Moved Permanently indicates that the resource has been assigned a new permanent URI and any future references should use one of the returned URIs.

Question 11: The HTTP status code for ‘I’m a teapot’ is:

1) 414
2) 418
3) 422
4) 426

Answer: B

Explanation: 418 I’m a teapot is an April Fools’ joke response code indicating the server refuses to brew coffee because it is, permanently, a teapot.