---
title: ShieldBackendConfiguration
summary: Configuration options for shield backends returned by Shield.encryptedBackend and Shield.unencryptedBackend.
url: https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/shielding/interface.ShieldBackendConfiguration/
---

**Kind:** Interface  
**Module:** [shielding](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/shielding/)  
**Package:** @fastly/js-compute 4.0.1  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/shielding.d.ts#L8

Configuration options for shield backends returned by
[Shield.encryptedBackend](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/shielding/class.Shield/#method-encryptedBackend) and [Shield.unencryptedBackend](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/shielding/class.Shield/#method-unencryptedBackend).

## Properties

### firstByteTimeout

**Type:** `number`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/shielding.d.ts#L12

First byte timeout for the returned backend, in milliseconds.