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AWS Solutions Architect · Lesson

Reliability and Performance Efficiency Pillars

Design for automatic recovery, horizontal scaling, and capacity management; choose the right resource types and monitor to maintain performance over time.

Reliability Pillar Overview

The Reliability pillar of the Well-Architected Framework ensures that a workload performs its intended function correctly and consistently when expected to. Reliability encompasses three areas: foundations (service limits, network topology), workload architecture (distributed systems, avoiding SPOFs), and change management and failure management (monitoring, scaling, recovering from failure). The goal is to build systems that recover automatically from infrastructure or service disruptions.

# Reliability design principles:
# 1. Automatically recover from failure
# 2. Test recovery procedures
# 3. Scale horizontally to increase availability
# 4. Stop guessing capacity (use auto scaling)
# 5. Manage change in automation (IaC + CI/CD)

# Key AWS services for reliability:
# - Auto Scaling Groups
# - Elastic Load Balancing
# - Route 53 health checks
# - AWS Backup

Service Limits and Quotas

AWS enforces service quotas (formerly limits) on resources to protect all customers. For example, default EC2 instance limits per region, VPC limits, and Lambda concurrent executions. If your workload unexpectedly hits a quota, requests will be throttled or rejected, causing reliability failures. Use Service Quotas console or CLI to view current limits and request increases before you need them. Monitor usage metrics to detect when you are approaching limits before they affect availability.

# List service quotas for EC2
aws service-quotas list-service-quotas \
  --service-code ec2 \
  --query 'Quotas[?QuotaName==`Running On-Demand Standard (A, C, D, H, I, M, R, T, Z) instances`]'

# Request quota increase
aws service-quotas request-service-quota-increase \
  --service-code ec2 \
  --quota-code L-1216C47A \
  --desired-value 500

All lessons in this course

  1. Operational Excellence and Security Pillars
  2. Reliability and Performance Efficiency Pillars
  3. Cost Optimisation and Sustainability Pillars
  4. Well-Architected Tool and Review Process
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