Ask HN: How to survive indefinite DDoS attack?

That probably depends on who your customers are. I can chime in one one scenario but maybe this does not help your case. If you are B2B then you could just shut off all public IP's and set up some Anycast VPN WAN accelerated meshes with your customers and use a wildcard sub-domain for each customer to access. They won't like having to set that up on their end but then they will have more resilience, privacy and security than they had before in that they can route around internet problems that would have otherwise caused outages or degraded services. Your company would have to provide professional services to help them with the setup and the customers would need discounts to offset the costs of the hardware assuming they do not already have it. The customers end-user devices would join their network over their VPN, not yours. For some B2B arrangements this isn't even a rounding error and removes scrubbing center costs and removes some SLA breach credits. Give this text to your principal network engineers, approve the spend and they will know what to do.

For the customers that do not accept this option, update the contracts and SLA's, then give them a public end-point that has a "best effort" SLA or use a cheap CDN if your contracts permit sending your sensitive data through them. Incentivize them to move to your Anycast VPN WAN accelerated mesh with tighter SLA's and improved security posture by keeping sensitive data off third party data processors like CDN's.

[Edit] This would also be a good time to use one of your companies sub-divisions or set up a new legal entity and get a new AS number with some dedicated IPv6 space and let your attackers just keep attacking the old address space. Announce the old IPv4 addresses on a throw away circuit to gather stats for law enforcement and network mailing lists. Try to do as much mesh peering with that new IPv6 space as you can. This is not security through obscurity so to speak, but rather a small piece of The Art of War.

The marketing team will not be happy but they can distribute their sites to a myriad of CDN's on marketing specific domains for your company. Gotta keep 'em separated, set some smart cache control headers and hope for the best.

An alternative to this semi-complex setup is to pay DDoS scrubbing centers to handle the routing of your datacenter traffic but that can hurt latency sensitive applications. This may be useful for the occasional extortion attack but would be very expensive and sub-optimial(c) in a never-ending indefinite DDoS attack.