You're thrown a typical webdev task, like setting the filesize limit for user uploads.
That's a web server configuration, not a programming issue.
Connect to MySQL and store some data.
(with-database (db '("host" "db" "user" "pass") :database-type :mysql)
(insert ...))
Now determine the dimensions of a jpeg image.
CL-GD has image-width and image-height functions. http://weitz.de/cl-gd/
And parse some JSON from a file.
In my world, json is rarely read from disk files. It's passed around between client and server. At any rate.
(with-open-file (file path)
(let ((json-buffer (file-length file)))
(read-sequence json-buffer file)
(decode json-buffer)))
You are showing a complete misunderstanding of software engineering. You don't go running around looking for examples and installing 3rd party packages willy nilly. Weird problems don't just "arise" out of the blue, and although there is some urgency to things there is never any chaos. Things are a bit more controlled, and you are assumed to know what you're doing, Lisp or otherwise.
You're thrown a typical webdev task, like setting the filesize limit for user uploads. Quick, how much time will it take in CL? Connect to MySQL and store some data. How many minutes, how many lines of code, how many libraries downloaded? Now determine the dimensions of a jpeg image. And parse some JSON from a file. Faster! (In PHP we haven't even left the standard library yet. It's that perfectly tailored for what web people do.) A weird problem arises, what's the chance that some PHP user had it before and wrote it up, compared to CL user? Something more complex: HTTP request goes in, ping to payment system goes out, file starts downloading with correct mimetype, where do you go for working code examples? You need to move your app to another webhost, how much hassle will it take? Client needs a CMS, which one do you pick, and how often does it get security updates? You make your app open source and people want to install it, what instructions do you give them?
Yes dammit, let's get practical. Let's get our hands dirty. I love this stuff.