Drupal Core APIs

Core Protocols & Architecture

SMTP (Simple Mail Transfer Protocol) is the fundamental protocol for sending email. Your application acts as an SMTP client, connecting to an SMTP server (port 25, 587, or 465) to submit messages. Port 587 with STARTTLS is the modern standard for submission.

Key flow: Your app → SMTP server → Recipient's mail server → Recipient's inbox

Here's a comprehensive picture of where Drupal frontend is right now and where it's heading:

1. The Big Split — Coupled vs Headless/Decoupled

The most important trend is the industry dividing into two distinct camps:

Traditional coupled Drupal — Drupal renders HTML via Twig templates, serves pages directly. Still the right choice for most sites.

Moving from Views to a Custom Controller or Block Plugin is a classic "Performance vs. Convenience" trade-off in Drupal. While Views is incredibly powerful, it is essentially a massive SQL generator and thermal-processing engine wrapped in layers of abstraction.
The "Views Overhead": Why it's Slower
When you use a direct query in a controller, you are telling the database exactly what you want. When you use Views, Drupal has to:
* Load the View Entity: Fetch the configuration (YAML).

In Drupal 11, the caching system is one of the most sophisticated parts of the architecture. It is designed to solve a specific problem: PHP is slow, but the database is even slower.
To understand the difference between the layers, it helps to look at them as a series of "gates." If a request can be answered at an early gate, Drupal doesn't have to do the heavy lifting of building the page.
1. The Hierarchy of Cache Layers
Drupal 11 uses a "layered" approach. When a user requests a page, Drupal checks these caches in order:
Layer A: Production/External Cache (Varnish/CDN)

In Drupal 11, bundle and content type are related but distinct concepts:

Content Type vs Bundle

Content Type is a specific type of bundle used for Node entities only. When you create a content type like “Article” or “Page” in the Drupal UI, you’re creating a bundle of the Node entity type.

Bundle is the broader, more generic term that applies across all fieldable entity types in Drupal. It’s a subtype or variation of an entity type that can have its own set of fields.