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date: 2025-07-28 topics: [nodejs, mongodb, social-graph, backend, devflow] day: 12

📘 Day 12 – Built a Follow/Unfollow System like Twitter 🧠

✅ What I Worked On

Today I completed a full Follow/Unfollow feature for DevFlow — simulating how apps like Twitter manage social relationships.

Feature	Status
➕ Follow a user	✅ Done
➖ Unfollow a user	✅ Done
📈 Get followers list	✅ Done
📉 Get followings list	✅ Done
🧠 Prevent duplicate follows	✅ Handled

💡 How It Works

🧾 MongoDB Schema Design

Each user document includes:

{
  _id: ObjectId,
  username: "sangam",
  followers: [ObjectId],   // who follows you
  following: [ObjectId],   // who you follow
}

📌 Updates are atomic using $addToSet (no duplicates) and $pull to remove.

🔄 Follow/Unfollow Logic

• Follow:

  • Add target user's ID to currentUser.following
  • Add current user ID to targetUser.followers

• Unfollow:

  • Pull IDs from both arrays

📦 Controller Endpoints

• POST /api/v1/users/:id/follow
• DELETE /api/v1/users/:id/unfollow
• GET /api/v1/users/:id/followers
• GET /api/v1/users/:id/followings

🔐 Security Notes

• Middleware ensures user is authenticated
• Validations prevent self-following or duplicates

📸 Snapshot

❌ Blockers

• Needed to resolve circular update risk between both users
• Indexed followers and following fields for faster queries

🧠 Reflection

This may seem like a small feature, but it's core to any social app. I learned how to handle:

• Mutual updates between collections
• Preventing duplicate relationships
• Structuring efficient lookups

“Social graphs are just arrays — until you scale them.”

🔜 Next Steps

• Follow counts cache layer (optional)
• Show follow button on user profile (frontend)
• Eventually → notification triggers on follow

🔗 References / Code

• 💻 DevFlow GitHub Repo
• 💻 DevFlow Commit