AWS Lambda vs Fargate vs App Runner

• AWS offers multiple serverless/managed compute options for running application code without managing servers.
• Lambda is for event-driven functions, Fargate is for containerized workloads, and App Runner is for web applications and APIs with zero configuration.
• All three eliminate server management but differ in execution model, duration limits, and use cases.

Lambda vs Fargate vs App Runner Comparison

AWS Lambda

• Event-driven, function-as-a-service – runs code in response to events (S3, API Gateway, SQS, DynamoDB, etc.).
• Scales automatically to thousands of concurrent executions per second.
• Pay only for execution time – billed per millisecond with a generous free tier (1M requests/month).
• 15-minute maximum execution – not suitable for long-running processes.
• Supports Provisioned Concurrency to eliminate cold starts for latency-sensitive workloads.
• Lambda@Edge and CloudFront Functions for edge computing.
• Best for: event processing, API backends, data transformations, scheduled tasks, and glue logic.

AWS Fargate

• Serverless compute for containers – runs Docker containers without managing EC2 instances.
• Works with ECS or EKS as the orchestration layer.
• No duration limit – suitable for long-running services, background workers, batch jobs.
• Full VPC networking – each task gets its own ENI with security group control.
• Supports persistent storage via EFS for shared file systems.
• Fargate Spot for up to 70% savings on fault-tolerant workloads.
• Best for: microservices, APIs needing persistent connections, background processing, and containerized applications.

AWS App Runner

• Fully managed service – goes from source code or container to running web service in minutes.
• Zero infrastructure configuration – no load balancer, no cluster, no task definition to manage.
• Provides a managed HTTPS endpoint with automatic TLS certificate.
• Auto-deploys from GitHub repository or ECR on code push.
• Can pause instances when no traffic – lower cost than Fargate minimum.
• VPC Connector for private resource access (RDS, ElastiCache, etc.).
• Best for: web applications, REST APIs, and teams that want the simplest deployment experience.

When to Choose Which

• Choose Lambda – Short-lived event processing (<15 min), API backends with variable traffic, integrations between AWS services, cost optimization for sporadic workloads.
• Choose Fargate – Long-running containers, persistent connections (WebSocket, gRPC), complex multi-container applications, need full ECS/EKS ecosystem.
• Choose App Runner – Simple web apps/APIs, want fastest time-to-deploy, team unfamiliar with containers/orchestration, predictable HTTP request-response workloads.

AWS Certification Exam Practice Questions

1. A startup needs to deploy a REST API that handles unpredictable traffic spikes (0 to thousands of requests per second) and they want to pay nothing during idle periods. Which service is most cost-effective?
   1. App Runner
   2. Fargate with ECS
   3. Lambda with API Gateway
   4. EC2 with Auto Scaling
2. A team needs to run a containerized web application that maintains WebSocket connections and requires persistent EFS storage. Which compute option supports this?
   1. Lambda
   2. Fargate with ECS
   3. App Runner
   4. Lambda with container image
3. A developer wants to deploy a Python web application directly from a GitHub repository with automatic HTTPS, auto-scaling, and zero infrastructure management. Which service requires the least configuration?
   1. Lambda with API Gateway
   2. Fargate with ALB
   3. App Runner
   4. Elastic Beanstalk

Related Posts

• AWS ECS vs EKS vs Fargate
• AWS ELB – ALB vs NLB vs GWLB
• AWS Certified Solutions Architect – Associate Exam Learning Path

References

AWS Lambda Developer Guide

AWS Fargate Documentation

AWS App Runner Developer Guide