I like to combine those:

    const RESEND_DELAY_MS = ONE_HOUR_IN_MS;

Having the unit in the name saved me more than once and having non-contextual constants for sizes increases readability imo.

I do this instead:

    const RESEND_DELAY_MS = 1 * 60 * 60 * 1000;  // one hour

Essentially the same, but the lack of extra variable spares one jump. Also you can change it without introducing a new variable (no dependency).

Better yet:

    const ONE_HOUR_IN_MS = 3600000
    const RESEND_DELAY = ONE_HOUR_IN_MS

I don't get why this is better. My approach:

const RESEND_DELAY_MS = 3600000; // because TTL in Agora

I would even go for

const RESEND_DELAY_MS = 3600*1000; // because TTL in Agora

Easier to check for the right number of zeros

Yes full agree

I've used stuff like this to do:

const ONE_HOUR = 3600000;

const RESEND_DELAY_MS = 2.5 * ONE_HOUR; // because TTL in Agora

IMO it makes it easier for successor to fiddle with.