WordPress Essentials

GraphQL is a query language for APIs and a server-side runtime for answering those queries: a client asks for precisely the fields it needs from a typed schema, in one request, instead of calling several fixed endpoints and discarding most of what comes back.

Microservices is an architectural style in which one application is built as a set of small services, each running in its own process, owning its own data and talking to the others over lightweight network calls, so that each can be built, deployed and scaled on its own.

Continuous integration is the practice of every developer merging their work into a shared mainline at least once a day, with an automated build and test run on each merge, so that integration problems surface within minutes of being created rather than weeks later at release time.

A web server is the program listening on a network port for HTTP requests and answering them, either by returning a file from disk or by handing the request to application code behind it.

Load balancing is the practice of putting one entry point in front of several interchangeable servers and distributing incoming requests among them by a chosen policy, so that no single machine carries the traffic and no single machine's failure takes the service down.

A CDN is a worldwide network of servers that answers requests for your site from a location near the person asking, instead of sending every request back to the single machine your site runs on.