GraphQLSDLAdvanced~4h

GraphQL

Say what the server will do

A document asks for exactly what it needs and the answer arrives in the same shape. What that cost is a different question, and it has an exact answer: a resolver runs once per parent object, so a query four fields long can be eighty-five trips to the database. This is the whole execution model, drilled.

Start this project See the modules

Modules: 6
Drills: 13
Build steps: 1
Time: ~4h

Walk out able to

Read a schema and a document you have never seen and say what comes back, what a failure empties, and how many database queries it costs.

What you drill

Schemas and documents

What a type admits, and the rule that refuses a query.

Execution and writes

Where a value lands, where a null lands, write order

The N+1 count

The exact query count, before and after a loader.

Caching and REST

What a client store can answer, and what REST costs.

The pitch

What you practise, and what you leave with

Not an artifact — a reading speed. Thirteen procedures, plus one real schema you wrote against and broke on purpose.

You will practise

Spelling a document, and what a type admits
Response shape, null propagation, writes
Counting resolver calls, batched and not
Client caching, and REST by the numbers

Afterwards you can

Say which values a declared type admits
Trace a failure to the position it empties
Count the queries a document actually costs
Decide what a client store can answer

Modules

6 modules, 23 items

Lessons explain one idea. Drills repeat it until it sticks. Build steps make something that exists afterwards.

1
Schema, document, syntax
~44 min
Say what a declared type admits, write a document, and name what refuses one.
- LessonWhy ask for the shape you want4 min
- LessonRead a field declaration7 min
- DrillSay what the type admits8 min
- LessonRead a document7 min
- DrillWrite it by hand8 min
- DrillName the rule that rejected it10 min
2
One resolver per field
~36 min
Predict where a value lands, and how far a single failure reaches.
- LessonFollow one field down the tree7 min
- LessonWhen one resolver raises8 min
- DrillPlace the value in the answer9 min
- DrillFind what the null took with it12 min
3
Reads, writes and variables
~20 min
Run a document of writes in order, and say what each variable became.
- DrillRun the writes in document order11 min
- DrillCoerce the variables9 min
4
Count what it costs
~41 min
Produce the number a document costs, before and after a loader.
- LessonCount what one query costs9 min
- LessonWhat a loader changes6 min
- DrillCount the resolver calls13 min
- DrillCount them again with a loader13 min
5
Caching without URLs
~22 min
Decide whether the client can answer without the network, and what a write changed.
- DrillDecide what the store can answer12 min
- DrillSay what the write updated10 min
6
Against a resource API
~53 min
Count what a document replaces, run one yourself, then diagnose four cold.
- DrillCount the requests it replaces9 min
- DrillCount the fields nobody drew9 min
- Build stepQuery a real schema yourself15 min
- LessonDiagnose two failures cold10 min
- LessonDiagnose two more, cold10 min