serverless.EmptyServerless与.NET Core Amazon Lambda Web类模板的差异问询

Great question! Let’s break down how these two serverless architectures differ, plus clarify whether you still need API Gateway for either approach.

Core Architectural Differences #

1. Multi-Function Lambda Pattern (like serverless.DynamoDBBlogAPI) #

This is the "single responsibility" approach tailored for serverless:

• Each API operation maps to a separate Lambda function (e.g., GetBlogsFunction, AddBlogFunction, DeleteBlogFunction). Even if all handlers live in the same Function.cs file, each one gets deployed as its own distinct Lambda resource in AWS.
• CloudFormation creates individual Lambda functions for each handler, each with its own configurable settings (memory allocation, timeout duration, IAM permissions).
• Logic is split into small, focused units—each function only handles one specific task, no more, no less.

2. ASP.NET Core WebAPI on Lambda (like serverless.AspNetCoreWebAPI) #

This is like "lifting and shifting" your traditional WebAPI into a serverless container:

• Your entire WebAPI project is packaged into one single Lambda function. Every incoming API request gets routed to this single Lambda.
• The ASP.NET Core runtime runs inside the Lambda, handling request routing, middleware, and controller logic exactly as it would in a traditional web server environment.
• You keep your familiar WebAPI structure (controllers, routes, filters, middleware) with only minimal tweaks to adapt to Lambda’s execution model.

Do You Still Need API Gateway? #

Short answer: Yes, API Gateway is required for both approaches—it’s the public entry point that lets external clients access your serverless APIs. The difference lies in how it’s used:

• For the multi-function pattern: API Gateway acts as the primary router, mapping individual API endpoints directly to their corresponding Lambda functions. For example, GET /blogs triggers GetBlogsFunction, while POST /blogs triggers AddBlogFunction.
• For the single Lambda WebAPI: API Gateway forwards all requests to your single Lambda, and the ASP.NET Core routing system takes over to direct requests to the right controller action. Here, API Gateway is more of a "traffic cop" than a granular router.

Pros and Cons of Each Approach #

Multi-Function Lambda #

Pros

• Granular control: Configure resources (memory, timeout) and permissions per function. For example, a delete function could have stricter IAM policies than a read-only function.
• Independent deployment: Update or roll back a single function without affecting the entire API, reducing deployment risk.
• Potential cost savings: Smaller functions may have lower cold-start overhead and only consume resources when their specific operation is called.

Cons

• Code fragmentation: Shared logic (like validation or DynamoDB utilities) needs to be extracted into shared layers, adding complexity.
• No ASP.NET Core ecosystem: You can’t use built-in WebAPI middleware (like authentication filters) out of the box—you’ll need to handle request/response mapping manually.

ASP.NET Core WebAPI on Lambda #

Pros

• Familiar development experience: Use your existing ASP.NET Core knowledge—no need to learn new patterns for request handling.
• Unified middleware and logic: Leverage the full ASP.NET Core ecosystem (logging, exception handling, identity) across all your endpoints.
• Clean code structure: Maintain a single, cohesive codebase that’s easy for teams used to WebAPI to navigate.

Cons

• One-size-fits-all configuration: All endpoints share the same Lambda memory, timeout, and concurrency limits—you can’t optimize for high-resource operations separately.
• Larger deployment footprint: Any change to a single endpoint requires redeploying the entire Lambda, which can increase deployment time and risk.
• Longer cold starts: Initializing the full ASP.NET Core runtime takes longer than starting a small, focused Lambda function, which might impact latency for infrequently accessed APIs.

内容的提问来源于stack exchange，提问作者Blake Rivell