No way to delegate Firebase token with v8 web SDK.

@thefastcat
Also, you should look at the Blaze plan, which is “pay as you go” - that’s what I use for my plans and my dev environment is typically $1.00/month since it’s only me causing bandwidth (and I don’t use large files). Depending on your production traffic and types of stored files, the blaze plan might be within your budget(I think unless you get a LOT of traffic will be less than $25/mo), not only do you get the external API calls, but you also get daily DB backups, which I think you should have for a production site anyway.