AWS US-EAST-1 outages cascade globally because most SaaS companies hard-coded their infrastructure to a single region

AWS's US-EAST-1 region (Northern Virginia) is the default region for most AWS services and the region where most SaaS companies deploy their primary infrastructure. When US-EAST-1 experiences an outage — like the October 2025 incident that lasted 15 hours and affected over 4 million users and 1,000+ companies — the blast radius extends far beyond the companies directly hosted there, because countless SaaS tools, APIs, and third-party services that other businesses depend on also go down. Why it matters: a single region outage takes down not just your own infrastructure but also your SaaS dependencies (auth, payments, monitoring, communication tools), so your incident response tooling itself may be unavailable during the outage, so you cannot even communicate with customers about the downtime, so customers lose trust and begin evaluating multi-cloud alternatives, so you face both immediate revenue loss and long-term customer churn from an event entirely outside your control. The structural root cause is that multi-region and multi-cloud architectures are 2-3x more expensive and complex to build than single-region deployments, so startups and mid-market SaaS companies rationally choose single-region to ship faster and cheaper — creating a systemic concentration risk that only becomes visible during a major outage.