apps/docs/content/troubleshooting/enabling-ipv4-addon.mdx
Enabling the IPv4 add-on will attach an IPv4 address to your project's compute instance, while preserving the existing IPv6 address. Both DNS records ref.supabase.co and db.ref.supabase.co will be updated to point to the IPv4 address.
Enabling the IPv4 add-on will not cause any downtime since existing connections will not be dropped. New inbound connections (both direct connections on ports 5432 and 6543, as well as PostgREST requests) will use the newly allocated IPv4 address.
No, the IPv4 add-on will not require a restart of the instance.
The IPv6 address will be preserved. New inbound connections (both direct connections on ports 5432 and 6543, as well as PostgREST requests) will use the newly allocated IPv4 address.
DNS changes do not affect already-established connections, and only new connections will resolve the updated record. For db.ref.supabase.co (i.e database connections through ports 5432 and 6543), the existing AAAA record will be updated to an A record pointing to the IPv4 address. This is essentially an in-place update for db.ref.supabase.co's value and record type which would externally translate to an AAAA removal and an A record creation, which mitigates against split moments in time where no record would be available.
Clients will use the new IPv4 address only after DNS propagation; until then, IPv6 continues to resolve and work for connectivity.
Removing the IPv4 add-on does tend to result in 'downtime' at a sub-minute time interval for database connections, given clients would've resolved the A record which now points to an unassigned IP address, and would need to wait for DNS propagation to go through in order for the AAAA record to be available