What is resiliency?

Resiliency is the ability of a system, service, or application to keep working correctly even when something goes wrong, like hardware failures, software bugs, or sudden spikes in traffic. Think of it like a rubber band that stretches when pulled but snaps back to its original shape without breaking.

Let's break it down

  • Redundancy: Having extra copies of critical components (servers, databases, network paths) so if one fails, another can take over.
  • Fault detection: The system constantly checks its own health to spot problems early.
  • Graceful degradation: If a part can’t work, the system reduces functionality instead of crashing completely.
  • Self‑healing: Automated processes that restart services, replace faulty parts, or reroute traffic without human intervention.
  • Scalability: Ability to add more resources quickly when demand spikes, preventing overload.

Why does it matter?

When users rely on an online service-shopping, banking, communication-they expect it to be available 24/7. Downtime can mean lost revenue, damaged reputation, and frustrated customers. Resiliency ensures continuity, protects data, and builds trust by minimizing interruptions.

Where is it used?

  • Cloud platforms (AWS, Azure, Google Cloud) for running web apps and databases.
  • E‑commerce sites that must stay open during sales events.
  • Financial systems handling transactions 24/7.
  • IoT networks where devices may lose connectivity intermittently.
  • Critical infrastructure like power grids, hospitals, and emergency services.

Good things about it

  • Higher availability: Services stay up longer, meeting strict uptime targets.
  • Better user experience: Fewer errors and slower load times.
  • Cost savings over time: Automated recovery reduces the need for manual emergency fixes.
  • Scalable growth: Systems can handle traffic spikes without a complete redesign.
  • Improved reliability: Reduces risk of data loss and service outages.

Not-so-good things

  • Increased complexity: Adding redundancy and self‑healing mechanisms makes architecture harder to design and maintain.
  • Higher upfront cost: More hardware, software licenses, and engineering effort are needed initially.
  • Potential over‑engineering: Building extreme resiliency for low‑risk applications can waste resources.
  • Monitoring overhead: Constant health checks generate extra traffic and require robust monitoring tools.
  • False sense of security: Even resilient systems can fail if not tested regularly; complacency can lead to missed bugs.