Design principles
The Well-Architected Framework identifies a set of general design principles to facilitate good design in the cloud for serverless applications:
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Speedy, simple, singular: Functions are concise, short, single-purpose, and their environment may live up to their request lifecycle. Transactions are efficiently cost-aware, and thus faster initiations are preferred.
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Think concurrent requests, not total requests: Serverless applications take advantage of the concurrency model, and tradeoffs at the design level are evaluated based on concurrency.
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Share nothing: Function runtime environment and underlying infrastructure are short-lived, therefore local resources such as temporary storage is not guaranteed. State can be manipulated within a state machine execution lifecycle, and persistent storage is preferred for highly durable requirements.
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Assume no hardware affinity: Underlying infrastructure may change. Use code or dependencies that are hardware-agnostic. CPU flags, for example, may not be available consistently.
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Orchestrate your application with state machines, not functions: Chaining Lambda executions within the code to orchestrate the workflow of your application results in a monolithic and tightly coupled application. Instead, use a state machine to orchestrate transactions and communication flows.
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Use events to trigger transactions: Events such as writing a new Amazon S3 object or an update to a database allow for transaction execution in response to business functionalities. This asynchronous event behavior is often consumer agnostic and drives just-in-time processing to achieve lean service design.
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Design for failures and duplicates: Operations triggered from requests or events must be idempotent, as failures can occur and a given request or event can be delivered more than once. Include appropriate retries for downstream calls.
