> ## Documentation Index
> Fetch the complete documentation index at: https://kweri.uchenna.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# QueryClient

> Low-level cache operations. Use Kweri directly unless you need fine-grained control.

`QueryClient` manages cache reads, writes, invalidations, and subscriptions. It is exposed as `kweri.queryClient` for advanced use cases — in most applications you'll interact with the `Kweri` facade instead.

## Constructor

```ts theme={null}
new QueryClient(store: CacheStore, observers: ObserverRegistry)
```

## Methods

### getQueryKey

```ts theme={null}
getQueryKey<E extends Endpoint>(endpoint: E, params: unknown): string
```

Returns the serialized cache key for an endpoint + params pair.

***

### invalidateQuery

```ts theme={null}
invalidateQuery<E extends Endpoint>(endpoint: E, params: unknown): void
```

Marks the entry for `endpoint + params` as stale by setting `updatedAt = 0`.

***

### invalidateByKey

```ts theme={null}
invalidateByKey(key: string): void
```

Invalidates by raw cache key string.

***

### invalidateByPath

```ts theme={null}
invalidateByPath(pattern: string | RegExp): void
```

Invalidates all entries whose key contains/matches `pattern`.

***

### removeQuery

```ts theme={null}
removeQuery<E extends Endpoint>(endpoint: E, params: unknown): void
```

Deletes the cache entry.

***

### removeByKey

```ts theme={null}
removeByKey(key: string): void
```

Deletes by raw key string.

***

### getCachedData

```ts theme={null}
getCachedData<E extends Endpoint>(endpoint: E, params: unknown): unknown
```

Returns cached data or `undefined`.

***

### setCachedData

```ts theme={null}
setCachedData<E extends Endpoint>(endpoint: E, params: unknown, data: unknown): void
```

Writes data into the cache and notifies observers.

***

### subscribe

```ts theme={null}
subscribe<E extends Endpoint>(
  endpoint: E,
  params: unknown,
  callback: (entry: CacheEntry) => void
): () => void
```

Subscribes to cache changes for a specific query.

## CacheStore

The underlying storage used by `QueryClient`. Exposed as `kweri.queryClient` → internal store.

```ts theme={null}
class CacheStore {
  get(key: string): CacheEntry | undefined
  set(key: string, partial: Partial<CacheEntry>): void  // merges
  delete(key: string): boolean
  has(key: string): boolean
  entries(): IterableIterator<[string, CacheEntry]>
  keys(): IterableIterator<string>
  values(): IterableIterator<CacheEntry>
  size: number
  clear(): void
}
```

## ObserverRegistry

Pub/sub registry for cache entry notifications.

```ts theme={null}
class ObserverRegistry {
  subscribe(key: string, callback: Callback): Unsubscribe
  notify(key: string, entry: CacheEntry): void
  subscribeAll(callback: GlobalNotifyCallback): Unsubscribe
  getObserverCount(key: string): number
  keys(): IterableIterator<string>
  size: number
  clear(key: string): void
  clearAll(): void
}

type Callback             = (entry: CacheEntry) => void
type Unsubscribe          = () => void
type GlobalNotifyCallback = (key: string, entry: CacheEntry) => void
```