Effective APIs

Points to remember in order to build robust APIs.

1. Validate date exists, not just the format.

Most date format validators only verify the structure of a date, but not the validity of the date itself.
In other words, the date 1989-02-29 would pass validation even 1989 is not a leap year.
Therefore, it’s a good idea to parse the date string into a date type and respond with a descriptive error in case an Exception is thrown.

Typically images are uploaded to an object store (S3 for example) and exposed through a content delivery network (e.g. cloudfront).
What I’ve seen in a few projects is the cloudfront or S3 URL of the image is stored in the database.
Caution needs to be exercised with this practice: it is possible that the data might be migrated from one object store to another; or exposed through a different CDN in order to reduce costs.
In such cases, developers would need to create a migration script to update the base URL of each image. Personally, I’m not a fan of this. I feel that replacing URLs is a fincicky operation. For example: you could end up with two slashes instead of one, or no slahes where there was supposed to be one. The task becomes tricker when you have a lot of data and the URLs stored might not all be the same format.
I believe the base URL should be sourced from a configuration file and concatenated when selecting the database row. The file name stored is a lot easier to validate (e.g. just ensure there is no slash at the beginning.)
```
SELECT CONCAT('https://cheapasscdn.com/AAF7-109EF9D259E/images/', avatar_file) AS avatar_url
FROM user;
```