## TL;DR

GraphQL schema design defines types, queries, mutations, and relationships. Best practices: design around business domain (not database schema), use Relay-style pagination (edges/nodes), avoid deeply nested queries (N+1 solved by DataLoader), version via evolution (add fields, deprecate old ones — never remove).

## Core Explanation

Types: Object types (User, Post), Scalar types (String, Int, Float, Boolean, ID), Enum types, Input types (for mutations), Interface/Union. Connections (Relay spec): `edges { node, cursor }`, `pageInfo { hasNextPage }`. DataLoader: batching + caching — solves N+1. Nullability: non-null `String!` vs. nullable `String` — prefer non-null unless field can legitimately be null.

## Further Reading

- [GraphQL Best Practices](https://graphql.org/learn/best-practices/)