typescript 44 lines · 7 steps

A tenant-aware HTTP cache in NestJS

Subclassing CacheInterceptor to key responses per tenant and read TTL from route metadata.

Explained by highlit

NestJS Intermediate caching interceptors multi-tenancy metadata inheritance

1import {
2  CACHE_MANAGER,
3  CacheInterceptor,
4} from '@nestjs/cache-manager';
5import {
6  ExecutionContext,
7  Inject,
8  Injectable,
9} from '@nestjs/common';
10import { Reflector } from '@nestjs/core';
11import { Cache } from 'cache-manager';
12import { Request } from 'express';
13 
14import { CACHE_TTL_METADATA } from './cache-ttl.decorator';
15 
16@Injectable()
17export class HttpCacheInterceptor extends CacheInterceptor {
18  constructor(
19    @Inject(CACHE_MANAGER) cacheManager: Cache,
20    protected readonly reflector: Reflector,
21  ) {
22    super(cacheManager, reflector);
23  }
24 
25  protected trackBy(context: ExecutionContext): string | undefined {
26    const request = context.switchToHttp().getRequest<Request>();
27 
28    if (request.method !== 'GET') {
29      return undefined;
30    }
31 
32    const tenant = request.headers['x-tenant-id'] ?? 'public';
33    return `${tenant}:${request.originalUrl}`;
34  }
35 
36  protected getTtl(context: ExecutionContext): number | undefined {
37    const handlerTtl = this.reflector.getAllAndOverride<number>(
38      CACHE_TTL_METADATA,
39      [context.getHandler(), context.getClass()],
40    );
41 
42    return handlerTtl ?? 30_000;
43  }
44}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Overriding trackBy lets you control exactly what counts as a unique cache key.
2Returning undefined from a cache key is the idiomatic way to opt a request out of caching.
3Reflector with getAllAndOverride reads per-handler metadata so config lives next to the route.

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