val CachingHeaders: <ERROR CLASS><CachingHeadersConfig>

A plugin that adds the capability to configure the Cache-Control and Expires headers used for HTTP caching. The example below shows how to add the Cache-Control header with the max-age option for CSS and JSON:

install(CachingHeaders) {
options { call, outgoingContent ->
when (outgoingContent.contentType?.withoutParameters()) {
ContentType.Text.CSS -> CachingOptions(CacheControl.MaxAge(maxAgeSeconds = 3600))
ContentType.Application.Json -> CachingOptions(CacheControl.MaxAge(maxAgeSeconds = 60))
else -> null

You can learn more from Caching headers.