Jonathan Sick added a comment - 22/Jun/20 8:23 PM I think we've cracked this. One change that needed to be be made was in the search app to always include a trailing slash in the path (i.e. /search/?query=vault) . Gatsby natively prefers trailing slashes. Before we were rewriting the browser URL with just the directory name (i.e. /search?query=vault ), but that actually triggers a 301 redirect on the client. Second, we've modified the Fastly Varnish configuration for directory redirects to access the index.html file in the S3 bucket if the path ends with a trailing slash. Before, the redirect VCL was: if ( req.url ~ "/$" ) { set req.url = req.url "index.html" ; } The new redirect VCL is: if ( req.url.path ~ "/$" ) { set req.url = req.url.path "index.html" } So the key parts of this are: Test if the path ends with "/" rather than the whole URL. This lets us be compatible with query strings. When setting the new req.url, append "index.html" to the path, which excludes the query string.