Networking & Delivery
IPv4 vs IPv6
The two versions of internet addressing: IPv4 addresses are scarce and increasingly billed for, while IPv6 is abundant and usually free.
IPv4 and IPv6 are the two schemes for addressing machines on the internet. IPv4 uses the familiar four-number format and has run out: there are only about four billion addresses, and they're all spoken for. IPv6 uses a vastly larger space, enough to give every device its own address forever, but adoption has been slow and some networks still don't route it.
The scarcity now shows up on your bill. Because IPv4 addresses are a depleted resource, providers increasingly charge a small monthly fee per public IPv4 address, while handing out IPv6 for free. AWS started charging for IPv4 in 2024, and others followed. It's a minor cost per server that adds up across a fleet.
For most deployments you still want an IPv4 address, because a meaningful slice of users can't reach IPv6-only services. The pragmatic setup is dual-stack: both addresses on the server, so everyone can connect, accepting the small IPv4 charge as the cost of universal reach.