GraphQL is aggressively becoming the new kid on the block when it comes to writing APi's.

Partly due to it’s ability to let clients query only the data they need at that moment and in the format that they need it.

A thread

For a couple of months now, I’ve been digging through GraphQl and the GraphQL schema Definition Language(SDL) which amplify uses, and here’s a breakdown on the basics of what I found out.

The first step in creating a GraphQL API is creating a schema that defines the capabilities of that API.

Here’s an example schema that has a user-defined type called Post with values.

The ID and String are known as scalar types.

There are other scalar types such as Int , Float, Bool etc.

The ! at the end of a scalar type marks that field as non-nullable.
It must always have a value.

A schema is composed of 2 types
1) root type
2) user-defined types.

We just created a user define type above, let’s take a look at root types.
1) Query(Read-only fetch).
Queries are used in fetching data from the data source and nothing else.

2) Mutation( write, followed by a fetch)
Used in making changes to your database. Returns a value when a change is made.

Subscription (long-lived connection for receiving data.) Subscriptions in AWS AppSync are invoked as a response to a mutation.

They help provide real-time capabilities to your api.

So the general form of a schema is

Resolvers
One of the concepts in GraphQL that took me a while to comprehend was Resolvers. I don’t know why, but it went over my head.
So here’s a straightforward explanation for it.

We just defined types above. User types and root types . Resolvers simply connects the fields of those types to a data source.
There are multiple data sources you can connect to.

A NoSQL database like DynamoDB, A relational database like Amazon Aurora, lambda functions.

There's still a ton of stuff to talk about with respect to GraphQL, here's a beginner introduction to GraphQL.