Multi-tier application architecture, including three-tier and n-tier models, has been fundamental in user-facing applications for decades. This architecture typically comprises:
Presentation Tier: The user interface component, like web pages and mobile app UIs.
Logic Tier: The code translating user actions into application functionality, such as database operations.
Data Tier: Storage solutions like databases, object stores, caches, and file systems holding application-relevant data.
This architecture ensures decoupled, independently scalable components, allowing for separate development, management, and maintenance, often by different teams.
Multi-tier applications often require creating standard components such as message queues, APIs, data models, and security protocols, which are essential but repetitive across different applications.
AWS streamlines the creation of multi-tier applications, especially serverless ones, reducing deployment complexity and server management overhead. Services like Amazon API Gateway and AWS Lambda simplify robust multi-tier application development. API Gateway’s integration with Lambda allows code functions to be triggered directly via HTTPS requests, scaling automatically with request volume.
Together, these services facilitate a serverless logic tier, letting developers focus on core application code rather than infrastructure concerns like high availability, scaling, or client authorization mechanisms. For serverless presentation and data tiers, AWS offers solutions like Amazon CloudFront, Amazon S3, Amazon Aurora, and Amazon DynamoDB.
Presentation tier
The presentation tier in AWS interacts with the logic tier through API Gateway REST endpoints accessible over the internet, allowing various clients like desktop apps, mobile apps, webpages, IoT devices, etc., to communicate with these endpoints. AWS offers several serverless options for the presentation tier:
Amazon Cognito
This service provides user identity and data synchronization, enabling user sign-up, sign-in, and access control in web and mobile apps. It's scalable to millions of users and supports sign-in with social and enterprise identity providers.
Amazon S3 with CloudFront
You can host static websites, like single-page applications, directly from S3, using CloudFront as a content delivery network (CDN) to enhance performance and implement SSL/TLS.
AWS Amplify
This set of tools and services helps developers build scalable full-stack applications. Amplify offers managed hosting for web apps with a reliable CDN, supports various web and mobile frameworks, and integrates CI/CD workflows. It may require CORS compliance for direct API invocations from webpages.
When deploying websites with CloudFront, you get a domain name for your application. You can use Amazon Route 53 for domain registration and to direct traffic to your CloudFront distribution or to assign custom domain names to your API Gateway distribution for familiar user access.
Logic tier
The logic tier in a three-tier architecture, crucially enhanced by Amazon API Gateway and AWS Lambda, offers a serverless, highly available, scalable, and secure alternative to traditional server-based models. Using these services eliminates the need for server management, reduces risks associated with provisioning, and simplifies the deployment and security of APIs.
AWS Lambda
Brings the convenience of not having to manage an operating system, servers, or worry about scaling issues. Lambda functions, triggered by events like HTTPS requests via API Gateway, handle the application's business logic. They allow for granularity in exposing application functionality and can interact with various dependencies, including other Lambda functions.
Amazon API Gateway
Serves as a robust platform for creating, publishing, and securing APIs at any scale, supporting both REST and HTTP APIs. It simplifies API performance optimization through caching and content delivery. API Gateway APIs consist of resources and methods, with each method potentially backed by a Lambda function. This setup allows for the modularization of application functionality, exposing it through REST endpoints.
Deployment of Lambda functions involves uploading code as a package to Amazon S3 or as a container image, with various deployment options like AWS Management Console, AWS CLI, or infrastructure as code tools. API Gateway and Lambda can be connected via proxy or non-proxy integrations, enabling seamless interaction between the presentation tier and the APIs.
Data tier
Using AWS Lambda for your logic tier offers flexibility in data storage options for the data tier. Lambda functions can connect to various data stores by incorporating the necessary database drivers in their deployment package, and securely access these stores using IAM roles or encrypted credentials via AWS KMS or AWS Secrets Manager.
AWS provides a range of both serverless and traditional data storage options, suitable for different application requirements:
Serverless Data Storage Options:
Amazon S3
An object storage service known for its scalability, data availability, security, and performance.
Amazon Aurora
A MySQL and PostgreSQL compatible relational database that balances enterprise database features with open-source cost efficiency. It offers both serverless and traditional models.
Amazon DynamoDB
A key-value and document database delivering high performance at any scale. It's fully managed, serverless, and supports multi-region, multi-active durability.
Amazon Timestream
A time series database ideal for IoT and operational applications, efficiently handling trillions of events per day at a fraction of the cost of relational databases.
Amazon Quantum Ledger Database (QLDB)
Provides a cryptographically verifiable transaction log, suitable for applications requiring a centralized, trusted authority.
Amazon Keyspaces (for Apache Cassandra)
A managed Apache Cassandra-compatible database service, offering serverless scalability and eliminating the need for server management.
Amazon Elastic File System (EFS)
A serverless file system that scales automatically, suitable for shared file storage in AWS Cloud and on-premises resources.
Non-Serverless Data Storage Options:
Amazon RDS
Simplifies setup, operation, and scaling of a relational database with multiple engine options.
Amazon Redshift
A fully managed data warehouse service, capable of handling petabyte-scale data.
Amazon ElastiCache
Manages Redis or Memcached for in-memory data stores.
Amazon Neptune
A fast graph database service for applications working with highly connected datasets.
Amazon DocumentDB
A MongoDB-compatible document database service.
Amazon EC2
Can run practically any database depending on Operating System, Licensing etc.
References
Conclusion - AWS Serverless Multi-Tier Architectures with Amazon API Gateway and AWS Lambda