What high availability means
A highly available application keeps working even when individual components fail, by avoiding single points of failure. On a cloud platform like AWS, you can design this without excessive complexity, but it requires thinking about every layer, not just one. A common mistake is making one part redundant and assuming the whole system is highly available. True high availability comes from resilience across the stack: application, data, and deployment, so a failure in any single place does not take the whole system down.
Multiple instances and health checks
Start with the application tier: run multiple instances across more than one location (such as multiple availability zones) so that if one instance or zone fails, others keep serving. Put a load balancer in front with health checks, so traffic is automatically routed only to healthy instances and away from failed ones. This combination, redundant instances plus health-checked routing, is the foundation of availability for the application layer, ensuring no single instance failure causes an outage.
Database resilience
The database is often the hardest part to make resilient and a common single point of failure. Use a database setup that can survive the loss of one node, such as a managed database with a standby that can take over automatically. Without database resilience, redundant application instances are pointless, since they all depend on that one database. Making the data tier resilient is essential, and often the most important and overlooked part of a genuinely highly available design.
Backups and object storage
Resilience is not only about live redundancy; it is also about recovery. Keep backups of your data so you can restore from accidental deletion, corruption, or disaster, since redundancy alone does not protect against these. Use durable object storage for files and assets, which is designed to be highly durable and available. Combining live redundancy with reliable backups and durable storage covers both staying up during failures and recovering when something is lost or corrupted.
Deployment rollback, and the whole picture
A frequent cause of outages is a bad deployment, so include the ability to roll back quickly to a known-good version, which protects availability during changes. Pulling it together: redundant instances, health checks, a resilient database, backups, durable storage, and safe rollback each address a different failure mode. The key insight is that redundancy at one layer does not make the whole system highly available; you must address each layer for the design to truly hold up.
The bottom line
Designing a highly available web application on AWS means running multiple instances across zones with health-checked load balancing, making the database resilient, keeping backups, using durable object storage, and enabling quick deployment rollback. Crucially, redundancy at one layer alone is not enough, each layer must be addressed. Understanding this helps you build a system that survives individual failures rather than one with a hidden single point of failure.
Related on Skillo
See also: Application load balancer vs reverse proxy: what is the difference?, What is database replication? Explained.
Sources
Published date reflects the original event date (2026-10-23). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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