The problem it solves
Serving bytes from nearer the visitor. If your audience is concentrated in one country and your server is in that country, a CDN adds complexity for very little gain.
What it also brings
Often more useful than the caching itself:
- Absorbing traffic spikes
- Basic DDoS mitigation
- TLS termination at the edge
- Simple image transformation
The configuration that bites
Caching a page containing personalised content. Set cache rules per path deliberately, and never cache anything behind a login.