Adding a line of text in the Overview page to talk about horizontal scaling.

Author: Oxyjun

src/content/docs/d1/index.mdx

@@ -25,6 +25,8 @@ Create new serverless SQL databases to query from your Workers and Pages project
 
 D1 is Cloudflare’s native serverless database. D1 allows you to build applications that handle large amounts of users at no extra cost. With D1, you can restore your database to any minute within the last 30 days.
 
+D1 is designed to be scaled out horizontally - we recommend creating multiple, smaller databases for your application.
+
 Create your first D1 database by [following the Get started guide](/d1/get-started/), learn how to [import data into a database](/d1/build-with-d1/import-export-data/), and how to [interact with your database](/d1/build-with-d1/d1-client-api/) directly from [Workers](/workers/) or [Pages](/pages/functions/bindings/#d1-databases).
 
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