Context Caching

To speed up applications, we end up caching data in memory to avoid repeated trips to the database. Since we create a new Context per request, we depend on the context cache (if available).

// hits database
const user = await User.loadX(viewer, id);
// hits cache
const user2 = await User.loadX(viewer, id);

For example, in the above, we will only hit the database once to load the data for the id.

As the request gets a lot more complicated, we see significant savings here since we could end up saving a lot of trips to the database.

We use DataLoader to batch and cache queries.

We'll dive deeper into how we handle queries later.

By default, all queries have context, learn more here.

clearing the cache

Anytime there's a write to the database, we clear the entire cache. It's possible there are clever things we can do to selectively clear the cache but that's not currently happening.

// hits database
const user = await User.loadX(viewer, id);
// hits cache
const user2 = await User.loadX(viewer, id);
// perform some write
await CreateFooAction.create(vc, input).saveX()

// hits datbase
const user3 = await User.loadX(viewer, id);

no context

If the Viewer has no context, all queries hit the database.

// vc. no context
const vc = new LoggedOutViewer();
// hits database
const user = await User.loadX(vc, id);
// hits database
const user2 = await User.loadX(vc, id);