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Key Strategies for Building a Robust Backend API Solution

Creating a robust backend API solution requires a strategic approach. Here are some key strategies to consider when planning an API/Backend Service:

  1. Input Validation: 
    1. Malformed Syntax: If the request violates protocol standards or contains typos or errors, it’s considered malformed. For example, missing required headers, parameters, or an improperly formatted request body could trigger a 400 error.
    2. Missing Required Parameters: When a specific parameter is essential for processing a request, and it’s absent, returning a 400 error is appropriate. For instance, if your web form requires an EstateId parameter, you can throw a 400 error if it’s not present.
    3. Invalid Parameter Values: If the client sends parameter values that don’t adhere to the expected format or constraints, a 400 error is suitable. For example, passing an invalid estateId value could trigger this error.

Remember that a 400 error indicates a client-side issue, so consider providing a clear error message to help users understand what went wrong. Whether you choose to display an error message or redirect to a search page depends on your application’s context and user experience goals.

  1. Input Authentication:

A 401 Unauthorized status code in a REST API indicates that the client tried to operate on a protected resource without providing the proper authorization1. Here are some scenarios when you might return a 401 error:

  1. Missing or Invalid Authentication: When the client doesn’t provide valid credentials (e.g., missing access token or expired token), returning a 401 is appropriate2.
  2. Incorrect Credentials: If the provided credentials (such as API keys, tokens, or basic authentication) are incorrect, a 401 response is suitable2.
  3. Expired or Revoked Tokens: When an access token has expired or been revoked, returning a 401 communicates that the client needs to re-authenticate3.

Remember to include a WWW-Authenticate header field in the response, which provides a challenge applicable to the requested resource

  1. Input Access Authorization:

A 403 Forbidden status code in a REST API indicates that the client is authenticated but lacks permission to access the requested resource1. Here are some scenarios when you might use a 403 error:

  1. Insufficient Permissions: When a user is logged in but doesn’t have the necessary permissions for a specific action, such as modifying a document or accessing a restricted endpoint, a 403 response is appropriate2.
  2. Rate Limiting: If a user exceeds their allowed rate limit (e.g., too many requests within a specific time window), returning a 403 error helps enforce rate limits3.
  3. Payment Required: In some cases, you might want to prompt the user to pay or upgrade their account. Alongside a 406 error (Not Acceptable), a 403 response can indicate insufficient account limits3.

Remember to provide clear error messages in the response body to help users understand the reason for the forbidden access

  1. Input Resource Integrity:

When designing a RESTful API, returning a 404 Not Found status code is appropriate in specific scenarios. Let’s explore when to use it:

  1. Resource Not Found: If a client requests a specific resource (e.g., /foos/5), and that resource doesn’t exist (e.g., no foo with ID 5), returning a 404 is expected. It indicates that the requested resource is missing.
  2. Malformed URI: When the URL path is incorrect (e.g., /food/1 instead of /foos/1), a 404 response is suitable. It signifies either a badly constructed URI or a reference to a non-existent resource.
  3. Multiple Resources Referenced: If a URI references multiple resources (e.g., /products/5), a simple 404 response doesn’t specify which resource was not found. To mitigate this, consider providing additional information in the response body to clarify what wasn’t found.

Remember that 404 indicates either a missing resource or a structural issue in the URI. Providing clear error messages helps API users understand the problem and improve their experience

  1. System Failures:

The 500 Internal Server Error is a HTTP status code that indicates an unexpected condition was encountered by the server, which prevented it from fulfilling the request. Here are some key points about when to throw a 500 Internal Server Error from an API:

Server-side issues: The 500 Internal Server Error is typically used to indicate that an unexpected condition was encountered by the server, and it prevented the request from being fulfilled. This error falls within the range of 5xx error codes, which signify issues on the server side.

Unpredictable errors: If the error is caused by anything other than the inputs explicitly or implicitly supplied by the request, then a 500 error is likely appropriate. So, a failed database connection or other unpredictable error is accurately represented by a 500 series error.

Unknown error conditions: This response is often used when the exact error condition is unknown or does not fit any other error condition1.

Not client-side errors: It is a server error, not a client error. If server errors weren’t to be returned to the client, there wouldn’t be created an entire status code class for them (i.e., 5xx).

Remember, when users encounter a 500 error, there is little they can do to resolve the issue themselves1. Therefore, it’s important to handle these errors properly on the server side and provide meaningful error messages whenever possible. If you want to differentiate between a handled and unhandled server exception, you may do that using logging (at the server side) or in the request body.