What side projects have you enjoyed the most?

AWS has something like 200+ service offerings. They are all made out of a core ~10 services (ec2, lambda, s3, dynamo, kms, iam, etc). But under those is another set of services which they do not offer as services.

A fun recent side project has been identifying and bootstrapping those services which, to avoid cyclical dependencies, must be implemented in a way which does not depend on ..anything. It has been fun. You need to manage root keys and certs, a config store to map all deployed infra, identity management, all with as thin a dependency tree as possible. It's also fun to do in ways which very deliberately isn't "at scale" at all. A single node can handle more load than you'll ever see.

(Edit: after looking at your profile, if you have a particularly good or favorite cake recipe(s) I should try, please share :) another favorite side project has been "baking")