How do you handle DataLoader cache invalidation and avoid serving stale data in NestJS?

Q: How do you handle DataLoader cache invalidation and avoid serving stale data in NestJS?

@Mutation(() => User) async updateUser( @Args('input') input: UpdateUserInput, @Context('usersLoader') loader: DataLoader , ): Promise { const updated = await this.usersService.update(input.id, input); // Option 1: clear so the next load fetches fresh from DB loader.clear(input.id); // Option 2: prime with the updated value — avoids another DB round-trip loader.prime(input.id, updated); return updated; } // Disable caching for a loader that must always be fresh const freshLoader = new DataLoader( async (ids: readonly number[]) => { return this.usersService.findByIds([...ids]); }, { cache: false }, // each load() call hits the batch function ); loader.clear(key) — removes a single cached key; next load() for that key will re-batch. loader.clearAll() — flushes the entire request-scoped cache. loader.prime(key, value) — pre-populates the cache with a known value to avoid re-fetching. prime() is more efficient than clear() after a write — you already have the updated value. cache: false — disables caching entirely; every load() call is included in the next batch.

Difficulty: 7/10

DataLoader caching, NestJS request scope, cache invalidation strategies

Use loader.clear(key) to remove a specific key from the cache after a mutation, or loader.prime(key, value) to replace the cached value with the updated object. Call clearAll() to flush the entire request-scoped cache. Set cache: false for operations where freshness is always critical.

DataLoader cache clear and prime after mutation

Cache management methods:

1
loader.clear(key) — removes a single cached key; next load() for that key will re-batch.
2
loader.clearAll() — flushes the entire request-scoped cache.
3

How do you handle DataLoader cache invalidation and avoid serving stale data in NestJS?

Difficulty: 7/10

DataLoader caching, NestJS request scope, cache invalidation strategies

Use loader.clear(key) to remove a specific key from the cache after a mutation, or loader.prime(key, value) to replace the cached value with the updated object. Call clearAll() to flush the entire request-scoped cache. Set cache: false for operations where freshness is always critical.

DataLoader cache clear and prime after mutation

Cache management methods:

1
loader.clear(key) — removes a single cached key; next load() for that key will re-batch.
2
loader.clearAll() — flushes the entire request-scoped cache.
3

How do you handle DataLoader cache invalidation and avoid serving stale data in NestJS?

Use loader.clear(key) to remove a specific key from the cache after a mutation, or loader.prime(key, value) to replace the cached value with the updated object. Call clearAll() to flush the entire request-scoped cache. Set cache: false for operations where freshness is always critical.

How do you handle DataLoader cache invalidation and avoid serving stale data in NestJS?

Use loader.clear(key) to remove a specific key from the cache after a mutation, or loader.prime(key, value) to replace the cached value with the updated object. Call clearAll() to flush the entire request-scoped cache. Set cache: false for operations where freshness is always critical.

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