Backend.md in fastly-4.0.0

- old
+ new
@@ -13,9 +13,10 @@
 | **first_byte_timeout** | **Integer** | Maximum duration in milliseconds to wait for the server response to begin after a TCP connection is established and the request has been sent. If exceeded, the connection is aborted and a synthethic `503` response will be presented instead. May be set at runtime using `bereq.first_byte_timeout`. | [optional] |
 | **healthcheck** | **String** | The name of the healthcheck to use with this backend. | [optional] |
 | **hostname** | **String** | The hostname of the backend. May be used as an alternative to `address` to set the backend location. | [optional] |
 | **ipv4** | **String** | IPv4 address of the backend. May be used as an alternative to `address` to set the backend location. | [optional] |
 | **ipv6** | **String** | IPv6 address of the backend. May be used as an alternative to `address` to set the backend location. | [optional] |
+| **keepalive_time** | **Integer** | How long to keep a persistent connection to the backend between requests. | [optional] |
 | **max_conn** | **Integer** | Maximum number of concurrent connections this backend will accept. | [optional] |
 | **max_tls_version** | **String** | Maximum allowed TLS version on SSL connections to this backend. If your backend server is not able to negotiate a connection meeting this constraint, a synthetic `503` error response will be generated. | [optional] |
 | **min_tls_version** | **String** | Minimum allowed TLS version on SSL connections to this backend. If your backend server is not able to negotiate a connection meeting this constraint, a synthetic `503` error response will be generated. | [optional] |
 | **name** | **String** | The name of the backend. | [optional] |
 | **override_host** | **String** | If set, will replace the client-supplied HTTP `Host` header on connections to this backend. Applied after VCL has been processed, so this setting will take precedence over changing `bereq.http.Host` in VCL. | [optional] |