Persisted queries

Apollo supports two separate but related features called automatic persisted queries (APQs) and persisted queries. With both features, clients can execute a GraphQL operation by sending an operation's ID instead of the entire operation string. An operation's ID is a hash of the full operation string. Querying by ID can significantly reduce latency and bandwidth usage for very large operation strings.

Hashed queries are also sent by default using HTTP GET instead of the default POST, making them easier to cache in your edge network.

Differences between persisted queries and APQs

The persisted queries feature requires operations to be registered in a persisted query list (PQL). This allows the PQL to act as an operation safelist made by your first-party apps. As such, persisted queries is a security feature as much as a performance one.

With APQs, if the server can't find the operation ID the client provides, the server returns an error indicating that it needs the full operation string. If an Apollo client receives this error, it automatically retries the operation with the full operation string.

If you only want to improve request latency and bandwidth usage, APQ addresses your use case. If you also want to secure your supergraph with operation safelisting, you should register operations in a PQL.

For more details on differences between persisted queries and APQ, see the GraphOS persisted queries documentation.

Implementation steps

Both persisted queries and APQs require you to configure how your client makes requests. If you intend to use persisted queries for safelisting, you also need to generate and publish an operation manifest.

We recommend you follow this order while implementing:

The rest of this article details these steps.

Persisted queries also require you to create and link a PQL, and to configure your router to receive persisted query requests. This document only describes the steps that need to be taken by the client to create a manifest of the client's operations and send persisted query requests. For more information on the other configuration aspects of persisted queries, see the GraphOS persisted queries documentation.

0. Requirements

You can use APQs with the following versions of Apollo Kotlin, Apollo Server, and Apollo Router:

• Apollo Kotlin (v1.0.0+)
• Apollo Server (v1.0.0+)
• Apollo Router (v0.1.0+)

Using persisted queries for safelisting has the following requirements:

• Apollo Kotlin (v3.8.2+)
• Apollo Router (v1.25.0+)
• GraphOS Enterprise plan

1. Generate operation manifest

The operation manifest acts as a safelist of trusted operations the Apollo Router can check incoming requests against. To generate the operation manifest, set operationManifestFormat to "persistedQueryManifest" in your Gradle script:

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// build.gradle.kts
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apollo {
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  service("api") {
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    packageName.set("com.example")
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    // Enable generation of the operation manifest
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    operationManifestFormat.set("persistedQueryManifest") 
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  }
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}

The operation manifest is generated during code generation. This happens automatically every time you build your project or you can trigger it manually by executing the generateApolloSources Gradle task.

The operation manifest is generated in build/generated/manifest/apollo/$serviceName/persistedQueryManifest.json, where $serviceName is "api" here. The resulting operation manifest looks something like this:

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{
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  "format": "apollo-persisted-query-manifest",
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  "version": 1,
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  "operations": [
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    {
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      "id": "e0321f6b438bb42c022f633d38c19549dea9a2d55c908f64c5c6cb8403442fef",
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      "body": "query GetItem { thing { __typename } }",
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      "name": "GetItem",
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      "type": "query"
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    }
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  ]
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}

2. Publish operation manifest

After you generate an operation manifest, you publish it to your PQL with the Rover CLI like so:

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rover persisted-queries publish my-graph@my-variant \
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  --manifest ./persisted-query-manifest.json

• The my-graph@my-variant argument is the graph ref of any variant the PQL is linked to.
  • Graph refs have the format graph-id@variant-name.
• Use the --manifest option to provide the path to the manifest you want to publish.

The persisted-queries publish command does the following:

1. Publishes all operations in the provided manifest file to the PQL linked to the specified variant, or to the specified PQL.

   • Publishing a manifest to a PQL is additive. Any existing entries in the PQL remain.
   • If you publish an operation with the same id but different details from an existing entry in the PQL, the entire publish command fails with an error.

2. Updates any other variants that the PQL is applied to so that routers associated with those variants can fetch their updated PQL.

As with generating manifests, it's best to execute this command in your CI/CD pipeline to publish new operations as part of your app release process. The API key you supply to Rover must have the role of Graph Admin or Persisted Query Publisher. Persisted Query Publisher is a special role designed for use with the rover persisted-queries publish command; API keys with this role have no other access to your graph's data in GraphOS, and are appropriate for sharing with trusted third party client developers who should be allowed to publish operations to your graph's PQL but should not otherwise have access to your graph.

Test operations

You can send some test operations to test that you've successfully published your manifests:

First, start your GraphOS-connected router:

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APOLLO_KEY="..." APOLLO_GRAPH_REF="..." ./router --config ./router.yaml
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2023-05-11T15:32:30.684460Z  INFO Apollo Router v1.18.1 // (c) Apollo Graph, Inc. // Licensed as ELv2 (https://go.apollo.dev/elv2)
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2023-05-11T15:32:30.684480Z  INFO Anonymous usage data is gathered to inform Apollo product development.  See https://go.apollo.dev/o/privacy for details.
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2023-05-11T15:32:31.507085Z  INFO Health check endpoint exposed at http://127.0.0.1:8088/health
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2023-05-11T15:32:31.507823Z  INFO GraphQL endpoint exposed at http://127.0.0.1:4000/ 🚀

Next, make a POST request with curl, like so:

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curl http://localhost:4000 -X POST --json \
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'{"extensions":{"persistedQuery":{"version":1,"sha256Hash":"dc67510fb4289672bea757e862d6b00e83db5d3cbbcfb15260601b6f29bb2b8f"}}}'

If your router's PQL includes an operation with an ID that matches the value of the provided sha256Hash property, it executes the corresponding operation and returns its result.

3. Enable persisted queries on ApolloClient

Once you've configured your code generation to include operation IDs, you can update your client to query by operation ID rather than the full operation string. This configuration is the same whether you're using APQs or persisted queries. Call autoPersistedQueries() on your ApolloClient.Builder:

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val apolloClient = ApolloClient.Builder()
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  .serverUrl("https://...")
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  .autoPersistedQueries()
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  .build()

Once APQs are enabled on your ApolloClient, hashed queries are sent by default.

You may want to disable automatic persisted queries for certain queries, for instance to avoid any caching when the data is updated often. To do that, set enableAutoPersistedQueries to false on the ApolloCall:

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apolloClient.query(myQuery).enableAutoPersistedQueries(false).toFlow()

Generating custom IDs for persisted queries

By default, Apollo uses Sha256 hashing algorithm to generate an ID for the query. To provide custom ID generation logic, use the operationIdGenerator option. It accepts an instance that implements the OperationIdGenerator interface (com.apollographql.apollo3.compiler.OperationIdGenerator) as the input. You can use this option to either specify a different hashing algorithm or to fetch the persisted query ID from a different location, for example, from a service or a CLI.

Example Md5 hash generator:

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apollo {
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  service("service") {
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    operationIdGenerator.set(object : com.apollographql.apollo3.compiler.OperationIdGenerator {
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      override val version = "my-md5-version1"
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      override fun apply(operationDocument: String, operationName: String): String {
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        return operationDocument.md5()
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      }
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    })
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  }
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}

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import com.apollographql.apollo3.compiler.OperationIdGenerator
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apollo {
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  service("service") {
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    operationIdGenerator = new OperationIdGenerator() {
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      String apply(String operationDocument, String operationName) {
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        return operationDocument.md5()
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      }
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      /**
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       * Use this version override to indicate an update to the implementation.
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       * This forces gradle to recompile models.
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       */
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      String version = "my-md5-v1"
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    }
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  }
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}

ID generator versioning

The result of the ID generator is cached. The cache is not updated when the implementation of the ID Generator changes. To indicate an update to the implementation of the ID Generator, change the version override as shown in the above example.