In Green Custard's 8th Friday talk, Filipe explores the subject of GraphQL. Topics covered: - What is GraphQL? - What is it trying to solve? - How does it work - Introspection - Problems - Future Green Custard is a custom software development consultancy. To discover more about their work and the team visit www.green-custard.com.

1. GraphQL
20th April 2018

2. What is GraphQL
● Not a database, library
● Language agnostic
● Query Language
● Specification, not an implementation
○ Created by Facebook
○ There is no install in https://graphql.org/ , you can choose whichever implementation

3. What is it trying to solve
● The high number of round-trip requests in applications

4. What is it trying to solve
● The high number of round-trip requests in applications

5. What is it trying to solve
● The high number of round-trip requests in applications

6. What is it trying to solve
● The high number of round-trip requests in applications

7. What is it trying to solve
● The amount of work required to produce pages
● Client
○ Create a new view
○ Update a new view
○ Change a view
● Server
○ Update endpoints
○ Create endpoints

8. How does it work
● Example

9. How does it work
● Query roots
○ Entry points to the database

10. How does it work
● Can I query name, location, and products?

11. How does it work
● Can I query name, location, and products?

12. How does it work
● Can I query name, location, and products?

13. Introspection
● Every graphQL server has a special `__schema` that exposes all the fields
and object types
● Create tools like:
○ Auto-documentation
■ Ask server what are fields and create docs
○ Static validation
■ You know beforehand if the query is valid
○ IDE integration
■ IDEs can auto complete and validate queries

14. Problems
● N+1 queries
○ Solution: batching, using loaders in schemas
● HTTP Caching
○ Solution: Replay/Apollo
○ These libraries cache data locally, minimizes amount of data requested, does `diff`
● Security - malicious queries, infinite loops
○ Solution: Timeouts, query depth (nothing is deeper than 10 levels), query complexity

15. Future
● Deferred queries
○ Send me name/description first
○ Split into different queries

16. Key takeaways
● Exposes the server
● Lets the client decide what they want
● Reduces code complexity
● Real time query validation