Backend Developer Assessment

You're building a community feed for Hyveon. Each community can have thousands of members posting content. Design the API and database schema for:

• Creating a post (text + image)
• Fetching the community feed (paginated, chronological)
• Liking a post

Write the API endpoints, request/response shapes, and the database tables you'd create. Explain your decisions.

A user joins 30 communities. When they open the app they see a "Home" feed — posts from all communities they've joined, sorted by time.

How do you build this efficiently? What happens at 1 million users each in 30 communities? Walk through the problem and your solution.

Write a Node.js/Express (or Go) endpoint: POST /communities/:id/posts

It must:

• Authenticate the user via JWT
• Validate the user is a member of the community
• Accept content (string, max 2000 chars) and optional image_url
• Save the post and return it

Write real code with error handling.

This query runs on every feed load and is getting slow:

SELECT posts.*, users.username, users.avatar
FROM posts
JOIN users ON posts.user_id = users.id
WHERE posts.community_id = $1
ORDER BY posts.created_at DESC
LIMIT 20 OFFSET $2

What's wrong with it? Fix it. Explain why.

A moderator reports a user is spamming posts. Build a rate limiting system. Where does the logic live? What limits do you set and why?

Users upload photos of any size. Describe the full pipeline from user taps upload → image appears in feed. Include storage, processing, and delivery.

You push a bug to production. All notifications are sending twice. You catch it 10 minutes later. Walk me through exactly what you do — in order.