Defying Serverless API Constraints (API Days 2025)

Discover practical solutions to real-world serverless constraints faced by engineering teams that builds API projects using popular patterns such as Micro-Lambdas, Lambdaliths and Moduliths. This presentation explores creative workarounds for common and rarely discussed limitations.

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1. Defying Serverless API Constraints Real-life Serverless Workarounds Allan Chua April 2025 L400 | Serverless | API Days 2025 Singapore
2. About Me • Serverless Since 2019 • AWS Community Builders • AWS Singapore UG Volunteer • Hands-on CTO @ Premier Fiduciary • 4X AWS Certified Allan Chua
3. This Presentation is About Serverless APIs Archetypes Constraints Solutioning Options Pros & Cons Analysis
4. What’s Covered AWS Lambda API Gateway SAM Rest APIs Cloud Formation Node JS
5. What’s Not Covered Event-Driven Architecture (EDA) TypeScript Storage Services
6. Serverless API Archetypes
7. Micro-Lambdas API Gateway GET /INVOICES GET /INVOICES/{ID} POST /INVOICES/{ID} GET /PAYMENTS GET /PAYMENTS/{ID} POST /PAYMENTS/{ID} Single purpose functions that serves requests for each REST endpoint. • Least Change Collisions on Code • Easier to Maintain • Easiest to Debug • Good for Small Apps and POCs • Shorter Cold Starts PROS • Code Conflicts on SAM file • Write tons of IAC YAML • Plenty of Cold Starts • Scaling Constraints CONS
8. Maximum Number of Resources Inside a Cloud Formation Stack 500 Accurate as of April 15, 2025
9. Gateway-Lambda Integration Anatomy Input Output Lambda Function Function Execution Role Function Invocation Permission
10. 5 API Gateway CF Resources (Stage, Deployment, Rest API, Domain Name, Path Mapping) Maximum # of APIs built on top of Micro-Lambdas per CF Stack ((500 – 5) / 3) = 165 Lambda Functions 1 API Function = 3 Resources 500 Max Resource Count
11. Max # of Resources Inside a Cloud Formation Stack Solutioning Options Refactor to Lambda-Lith Group Resources into Nested CF Stacks Split Resources into Logical Stacks Refactor to Modulith
12. Splitting Resources into Logical Groups Reactors/ BG Workers Lambda Functions APIs Lambda Functions API Gateway Core S3 SQS DynamoDB IAM Roles Do! Core, Reactors, BG Workers and APIs S3 SQS DynamoDB IAM Roles Don’t Lambda Functions API Gateway
13. Reactors/ BG Workers Lambda Functions APIs Lambda Functions API Gateway Core S3 SQS DynamoDB IAM Roles This is decent but… • Scaling Bottleneck at the Compute Stack CONS • Larger Max Resource Constraint • Faster Deployments • Makes Compute Layer Refactorable • Less Risk of Deleting DBs PROS
14. Ideal Solution Reactors/ BG Workers Lambda Functions Core S3 SQS DynamoDB IAM Roles Notification APIs API Gateway Payment APIs Invoicing APIs Billing APIs Auth APIs Notification APIs
15. But You Can't Reference API Gateways from another CloudFormation Stack when using SAM Problem since 2018
16. Nesting CloudFormation Stacks Superior Option for Scaling Reactors/ BG Workers Lambda Functions Payment APIs API Gateway Core S3 SQS DynamoDB IAM Roles Invoicing APIs API Gateway Auth APIs API Gateway Notification APIs API Gateway Correspondence APIs API Gateway Company APIs API Gateway
17. Maximum Number of API Gateways Accurate as of April 15, 2025 ACCOUNT-LEVEL | NON-ADJUSTABLE 600 Regional 120 Edge-optimized
18. Routes per API Gateway GATEWAY-LEVEL | SOFT LIMIT Accurate as of April 15, 2025 300 36K Edge Optimized APIs 180K Regional APIs
19. Maximum Number of IAM Roles per Account ACCOUNT-LEVEL Accurate as of April 15, 2025 1000 SOFT LIMIT 5000 HARD LIMIT
20. AWS Service Quotas Are Adjustable They are Not Portable
21. AWS Service Quotas Are Adjustable But Not Portable DEV UAT PRD “It Works in DEV Account“
22. Max # of API Gateways, IAM Roles, SAM Issues Solutioning Options Refactor to Lambda-Lith Merge APIs (Bounded Context) Refactor to Moduliths
23. Lambda-Lith GET /INVOICES GET /INVOICES/{ID} POST /INVOICES/{ID} POST /PAYMENTS/{ID} GET /PAYMENTS/{ID} GET /PAYMENTS https://middy.js.org/ https://hono.dev/ API Gateway ANY /{proxy+} GREEDY PATH (Catch-all / Wildcard) Just like our traditional APIs where a single server process is in-charge of responding to all endpoints in a REST API.
24. https://middy.js.org/ Middy
25. https://hono.dev/ HONO
26. API Routing Frameworks for AWS Lambda - AWESOME for strangler migrations - Lowest Barrier of Entry - Gets Rid of Micro-lambda Scaling Issues - Least YAML Coding - Faster Deployment - Frequent Warm Starts - Great for Medium-sized Apps PROS - Higher Risk of Breakage - Single Point of Failure - Harder to Debug - Slower Response Times - Heavy Cold Start - Simple CRUD functions gets loaded with heavier libraries CONS
27. Lambda Function Maximum Package Size (Zipped) FUNCTION-LEVEL | HARD-LIMIT Accurate as of April 15, 2025 250 MB
28. Modulith API Gateway ANY /PAYMENTS/{proxy+} ANY /INVOICES/{proxy+} ANY /PURCHASE-ORDERS/{proxy+} - Frequent Warm Starts - Awesome for Large-scale API Development - Smaller Blast Radiuses - Low YAML Amount - Low Barrier of Entry - Low IAM Role Count - Simple CRUD APIs don’t need to load heavy SDKs used by reporting APIs PROS - AKA Modular Monoliths - 1 API Gateway - 1 Greedy Path per Module - 1 Function for each Module - Duplicated Libraries Across Functions - Lower amount of code samples & literature CONS ANY /REPORTS/{proxy+} POST /PAYMENTS/{ID} GET /PAYMENTS/{ID} GET /PAYMENTS GET /INVOICES GET /INVOICES/{ID} POST /INVOICES/{ID} GET /PURCHASE-ORDERS GET /PURCHASE-ORDERS/{ID} POST /PURCHASE-ORDERS/{ID} GET /REPORTS GET /REPORTS/{ID} POST /REPORTS/{ID}
29. Code Samples https://github.com/allanchua101/defying-serverless-constraints-demo
30. Runtime Lifespan
31. Serverless Ops Myth “AWS will take care of trivial Ops work for my Lambda Functions”
32. Upgrading Function Runtimes Consumes Manpower Responsibility is Shared
33. NodeJS Runtime Calendar http://bit.ly/42X2cPW
34. NodeJS Runtime Block Function Creation Calendar Feb 2025 16 Oct 2025 18 Jun 2026 20 22 Jun 2027
35. Function Runtime Upgrades and Monitoring Required https://allanchua101.github.io/sana/
36. Helps you monitor function upgrade progress
37. GPU Enabled Inferencing APIs • Not supported as of April 2025 • AWS seems to be aware • Some customers mentioned AWS is working on them • Use AWS Batch or Container Services to Implement them.
38. Conclusion • Distributed your CF Resources into Logical Groups • Micro-lambdas are great for small projects and prototyping. • Lambda-lith offers low entry barrier to Serverless. • Modulith Offers Extreme Code-base Scaling • Runtimes Expire and Require Routine Upgrades
39. 5 Minutes Q&A Session