---
lang: en
title: 'API docs: graphql.graphqlbindings.pub_sub_engine'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/extensions/graphql
permalink: /doc/en/lb4/apidocs.graphql.graphqlbindings.pub_sub_engine.html
---

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[Home](./index.md) &gt; [@loopback/graphql](./graphql.md) &gt; [GraphQLBindings](./graphql.graphqlbindings.md) &gt; [PUB\_SUB\_ENGINE](./graphql.graphqlbindings.pub_sub_engine.md)

## GraphQLBindings.PUB\_SUB\_ENGINE variable

Binding key for the GraphQL pub/sub engine

<b>Signature:</b>

```typescript
PUB_SUB_ENGINE: BindingKey<PubSubEngine>
```

