Apex Developer Guide

Apex Developer Guide
Release Notes
Getting Started with Apex
Introducing Apex
What is Apex?
Understanding Apex Core Concepts
When Should I Use Apex?
How Does Apex Work?
Developing Code in the Cloud
Apex Development Process
Apex Quick Start
Writing Apex
Running Apex
Debugging, Testing, and Deploying Apex
Apex Reference
Appendices
PDF

Note: This release is in preview. Features described here don’t become generally available until the latest general availability date that Salesforce announces for this release. Before then, and where features are noted as beta, pilot, or developer preview, we can’t guarantee general availability within any particular time frame or at all. Make your purchase decisions only on the basis of generally available products and features.

How Does Apex Work?

All Apex runs entirely on-demand on the Lightning Platform. Developers write and save Apex code to the platform, and end users trigger the execution of the Apex code via the user interface.
Apex is compiled, stored, and run entirely on the Lightning Platform Apex is compiled, run, and stored entirely on the Lightning Platform

When a developer writes and saves Apex code to the platform, the platform application server first compiles the code into an abstract set of instructions that can be understood by the Apex runtime interpreter, and then saves those instructions as metadata.

When an end user triggers the execution of Apex, perhaps by clicking a button or accessing a Visualforce page, the platform application server retrieves the compiled instructions from the metadata and sends them through the runtime interpreter before returning the result. The end user observes no differences in execution time from standard platform requests.