GraphQL Fundamentals & Query Language

GraphQL was created internally at Meta in 2012 during the rebuild of Facebook's mobile applications. On mobile cellular networks, the traditional REST architectural pattern suffered from two major physics constraints:

1. Over-Fetching (Wasted Bandwidth & CPU):

When a mobile screen needs only a user's name and avatar_url, calling GET /v1/users/42 might return 80 database fields (biography, address, settings, preferences, metadata) totaling 60KB of JSON instead of 300 bytes. On slow mobile networks, parsing and transferring unused JSON drains battery and slows UI rendering.

2. Under-Fetching & Network Waterfalls:

To render a single feed screen, a REST client must make chained sequential network calls:

1. GET /v1/users/42 (Fetch user info)
2. GET /v1/users/42/feed (Fetch post IDs)
3. GET /v1/posts/101/author (Fetch author for each post)
4. GET /v1/posts/101/comments (Fetch comments)

Each round-trip incurs mobile network latency (50-150ms RTT), producing a sluggish multi-second page load.