[Hyperdrive] explain d1 & hyperdrive (#21100)

* [Hyperdrive] explain d1 & hyperdrive

* Update src/content/docs/hyperdrive/reference/faq.mdx

Author: thomasgauvin

src/content/docs/hyperdrive/reference/faq.mdx

@@ -15,6 +15,18 @@ Hyperdrive connects to your database using [Cloudflare's IP address ranges](http
 
 You can use this to configure restrictions in your database firewall to restrict the IP addresses that can access your database.
 
+### Does Hyperdrive support connecting to D1 databases?
+
+Hyperdrive does not support [D1](/d1) because D1 provides fast connectivity from Workers by design.
+
+Hyperdrive is designed to speed up connectivity to traditional, regional SQL databases such as PostgreSQL. These databases are typically accessed using database drivers that communicate over TCP/IP.
+Unlike D1, creating a secure database connection to a traditional SQL database
+involves multiple round trips between the client (your Worker) and your database server.
+See [How Hyperdrive works](/hyperdrive/configuration/how-hyperdrive-works/) for more detail on why round trips are needed
+and how Hyperdrive solves this.
+
+D1 does not require round trips to create database connections. D1 is designed to be performant for access from Workers by default, without needing Hyperdrive.
+
 ## Pricing
 
 ### Does Hyperdrive charge for data transfer / egress?