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Welcome to Viaduct

Viaduct is a GraphQL-based system that provides a unified interface for accessing and interacting with any data source. Built by Airbnb and battle-tested in production at scale, Viaduct is an open source data-oriented service mesh designed to help you build powerful, scalable applications with ease and confidence.
The Viaduct engine is production-ready and proven reliable at scale. The developer API is under active development, with clear guidance on API stability in the roadmap.

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Core principles

Three principles have guided Viaduct since day one and continue to anchor the project:

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Central schema

Viaduct serves a single, integrated schema connecting all of your domains across your company—the central schema. While that schema is developed in a decentralized manner by many teams, it’s one highly connected graph. This unified approach eliminates the complexity of managing multiple schemas and provides a consistent interface for all your data.

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Hosted business logic

Teams host their business logic directly in Viaduct. This runs counter to what many consider to be best practices in GraphQL, which suggest that GraphQL servers should be a thin layer over microservices that host the real business logic. Viaduct is a serverless platform for hosting business logic, allowing you to focus on writing business logic rather than on operational issues.

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Re-entrancy

At the heart of Viaduct’s developer experience is what we call re-entrancy: logic hosted on Viaduct composes with other logic hosted on Viaduct by issuing GraphQL fragments and queries. Re-entrancy is crucial for maintaining modularity in a large codebase and avoiding classic monolith hazards.

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Key features

Type-safe resolvers

Write business logic with generated Kotlin classes that provide compile-time safety and IDE autocomplete

Schema-first development

Define your API with GraphQL schemas and let Viaduct generate the code you need to implement it

Modular architecture

Build tenant modules that can depend on each other and compose together through re-entrant queries

Built-in pagination

Implement cursor-based pagination with Relay Connection specification support out of the box

Global IDs

Type-safe identification for Node objects with GlobalID<T> types that embed both type and ID

Fast iteration

Development server with GraphiQL and auto-reloading for rapid prototyping and testing

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How Viaduct works

Viaduct applications follow a simple pattern:
  1. Define your schema - Write GraphQL schemas with @resolver directives to mark fields that need business logic
  2. Generate code - Viaduct generates GraphQL Representational Types (GRTs) and resolver base classes
  3. Implement resolvers - Extend the generated base classes and implement the resolve function
  4. Execute queries - Create a Viaduct engine instance and execute GraphQL operations
Here’s a simple example:
schema.graphqls
extend type Query {
  greeting: String @resolver
}
GreetingResolver.kt
import viaduct.api.Resolver
import com.example.viadapp.resolvers.resolverbases.QueryResolvers

@Resolver
class GreetingResolver : QueryResolvers.Greeting() {
    override suspend fun resolve(ctx: Context): String {
        return "Hello, World!"
    }
}
ViaductApplication.kt
val viaduct = BasicViaductFactory.create(
    tenantRegistrationInfo = TenantRegistrationInfo(
        tenantPackagePrefix = "com.example.viadapp"
    )
)

val result = viaduct.execute(
    ExecutionInput.create(
        operationText = "{ greeting }",
        variables = emptyMap()
    )
)

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Get started

Quickstart

Get up and running in minutes with the CLI starter demo

Installation

Set up Viaduct dependencies in your Gradle project

Core concepts

Understand resolvers, GRTs, and the Viaduct execution model

API reference

Explore the complete Viaduct API documentation

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Why Viaduct?

Viaduct is designed for teams building complex, data-intensive applications that need:
  • Unified data access - Single GraphQL API across all your services and data sources
  • Type safety - Kotlin’s type system ensures correctness at compile time
  • Scalability - Proven in production at Airbnb serving millions of requests
  • Developer productivity - Code generation eliminates boilerplate and catches errors early
  • Modularity - Build and deploy tenant modules independently while maintaining schema cohesion
Check out the demo applications to see Viaduct in action, from simple CLI tools to full-featured web services.

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Community and support

Viaduct is an open source project committed to fostering an inclusive and collaborative community where external developers can contribute, innovate, and help shape the future of data-oriented development.
The Viaduct developer API is under active development. Check the roadmap to see which parts of the API are more or less subject to future change.

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