Idk what kind of software you work on but in my slice of the B2B SaaS world, 5 minutes of downtime during business hours would generate 100s of support tickets with very angry users letting us know they couldn’t do their job.
Perhaps part of the answer is that if you're a solo founder who is staying solo, try not to create a business where you have these kinds of dynamics.
OR, if you are creating one that does, scale up past being solo ASAP.
Your support ticketing system and company web presence are two I can think of. I provide the ticketing service myself but I outsource my web presence (the landing page not the app) to a third party service. My thought is the web site should never go down. If the ticketing system is down it means things are beyond hosed :)
I doubt you're trying to solve the same problems as the GP at that scale, or probably even the same types of problems.
Maybe 400 businesses each with 10+ employees and 10,000+ customers (who also had access to the platform). It was too much and I regret not hiring sooner.
Another thread mentioned here that hiring someone you trust enough to own problems when you’re unavailable is daunting. I concur with that.
FWIW, that sounds like an interesting story/case study, if you're willing to share some time. I'm not surprised by your conclusion, but I'm quite impressed if you managed to scale even tolerably well to that level before bringing in some extra help.