From serverless to functionless

Examples of functionless (a.k.a. Lambda-less) integration pattern, where a direct integration between two AWS services is configured instead of using custom code in an intermediary Lambda function, based on Step Functions, AppSync, EventBridge.

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1. Baltic Sep 10, 2025
 Gdynia, Poland

2. From serverless to functionless Jakub Gaj Cloud Solution Architect @ Danske Bank
 Copenhagen, Denmark Baltic
3. Baltic If your Lambda function is not performing custom logic while integrating with other AWS services, chances are that it may be unnecessary. Use serverless functions to transform data, not to transport data between services.
4. Baltic FUNCTIONLESS What if you could build your next serverless application without a single Lambda function?
5. What is the functionless architecture? Type of serverless architecture emphasizing event-driven, service-based design without the need to write, package, deploy, and manage countless individual serverless functions or microservices. Nintendo characters/images © Nintendo. Non-commercial use.
6. ๏ Build around events initiating some actions ๏ Actions can be handled by variety of services ๏ No need for individual functions Event-Driven Everything ๏ AWS provides variety
 of managed services ๏ Play central role in functionless model ๏ Abstract away much of operational complexity Managed Services ๏ Workflows streamlined
 through managed services ๏ Simplifying complex business processes ๏ Simpler codebase Streamlined Workflows Key characteristics of functionless model
7. Scalability Functions scaled automatically with the number of requests Cost efficiency Billed based on the execution time and compute resources consumed Fast deployment Quick iteration and deployment of functions code Reduced operations Eliminating servers management, automatic scaling Key advantages of Lambda functions Nintendo characters/images © Nintendo. Non-commercial use.
8. Cold start latency Time required
 to initialise the function with no recent invokes Hidden costs Over-provisioned functions, related resources (CloudWatch Logs) Extra libraries Deployment of extra libraries and dependencies Debugging Troubleshooting, debugging, coordinating logs and tracing across multiple functions Key disadvantages of Lambda functions Nintendo characters/images © Nintendo. Non-commercial use.
9. Cold start latency Extra costs Extra libraries Debugging Mitigations to these disadvantages Reserved / provisioned concurrency Compute savings plans, CloudWatch Logs retention Deployment frameworks like AWS SAM, AWS CDK Good error handling, logging libraries, logs aggregation Nintendo characters/images © Nintendo. Non-commercial use.
10. Migration strategy for serverless applications Step Functions workflows Monolithic
 Lambda functions Microservice-style serverless app Nintendo characters/images © Nintendo. Non-commercial use.
11. Core managed services for functionless EventBridge
 Serverless events router (custom buses, rules) Step Functions Serverless work fl ow orchestration (state machines) AppSync
 Serverless GraphQL and
 pub/sub APIs Serverless RESTful and WebSocket APIs API Gateway
12. Baltic SUPER MARIO POST A functionless application in action
13. Super Post
 Event Bus Super Post
 Event Bus Letter Dispatch
 State Machine Letter Collect
 State Machine Super Mailbox
 DynamoDB Global Table Super Scoreboard
 DynamoDB Global Table Nintendo characters/images © Nintendo. Non-commercial use. Super Mario Princess Peach
14. Nintendo characters/images © Nintendo. Non-commercial use.
15. 1. Create map run from JSON array (S3 object) 2. Validate document type is LOVE_LETTER 3. Generate new Letter ID (UUID v4) 4. Add new items to DynamoDB global tables 5. Create formatted event with Letter data 6. Send combined events to local Event Bus 7. Event Bus emits events to remote Event Bus Dispatch Letters (Mario)
16. 1. Delay workflow execution (get ready) 2. Validate letter is NEW and it’s a LOVE_LETTER 3. Get reaction emoji from Secret Manager 4. Add verification parameters to Letter data 5. Update records in DynamoDB global tables 6. Send event to local Event Bus for logging Collect Letters (Peach)
17. Baltic DEMO Time for a quick demo of Super Mario Post
18. Baltic GOTCHAS Limitations of the functionless model
19. ๏ Fine for simpler workflows ๏ Complex logic will produce complex workflows ๏ Easier to code in one
 of supported languages Limitations of ASL ๏ Some services require transforming JSON data to consumable format ๏ Need for data validation ๏ Example: DynamoDB Data Marshalling ๏ Bundling of external libraries into Lambda functions or layers ๏ Example: Prisma Client for connecting to RDS databases External Libraries Does functionless model make any sense?
20. Baltic KEY TAKEAWAYS Reimagine your serverless applications
21. Single purpose functions Orchestration Efficient processing Design principles for serverless applications AWS Well-Architected:
 Security Pillar
 Cost Optimisation Pilar AWS Well-Architected:
 Reliability Pillar
 Performance Efficiency Pilar AWS Well-Architected:
 Reliability Pillar
 Performance Efficiency Pilar Functions should be compact, short, and single purpose. Each function taking care of speci fi c task. Orchestrate your application with state machines, not functions. Use AWS SDK integrations with AWS services. Use events for triggering asynchronous, just-in-time processing. Design for failure and duplicates.
22. 🇬🇧 Thank you! 🇵🇱 Dziękuję! Let’s connect! Social Profiles Tech Blogs GitHub Repos Resources / Slides Jakub Gaj Super Mario, Princess Peach, and related characters, images, and design elements are © Nintendo. Used here for non-commercial, educational presentation. Not affiliated with or endorsed by Nintendo.