My understanding of how API works is

this.api = new sst.Api(this, "Api", {
      customDomain: {
         hostedZome: <http://myCoolSite.com|myCoolSite.com>,
         domainName: <http://api.myCoolSite.com|api.myCoolSite.com>,
         domainAlias: <http://www.api.myCoolSite.com|www.api.myCoolSite.com>,      
      }),

Will create an A record in route53 so you can request that api as

<http://api.myCoolSite.com|api.myCoolSite.com>

. then if you wanted to access that in a front end

const reactApp = new sst.ReactStaticSite(this, "ReactSite", {
      path: "frontend",
      environment: {
        REACT_APP_API_URL: this.api.url,

My expectation was that

this.api.url

would return

<http://api.myCoolSite.com|api.myCoolSite.com>

. Is that the expected behavior?

this.api.customDomainUrl

will give u that

Oh that might explain why it doesn’t work