Replit.com is an awesome new browser-based IDE where you can code alone or collaboratively with friends using their multiplayer features, particularly useful for education and sharing code examples with others. It supports a ton of different languages and execution environments, including a simple key-value store for persisting data. Replit users can interact with Supabase, a relational database that allows direct access to larger amounts of data from their repl, using supabase-js. To start, users sign up for Replit, create a new Node.js repl, import the `createClient` method, and set up a Supabase project with the URL and anon key. They can then query their countries table using SQL or JavaScript syntax, such as async/await syntax, and explore examples like querying by country name, ID, or ISO code. The blog provides additional challenges and full solutions for learning more about the query interface.