What is AWS Lambda?
AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. Lambda automatically manages the underlying infrastructure – including server maintenance, capacity provisioning, scaling, and patching – so you can focus on your application logic.
Lambda provides two compute primitives, each designed for different workload patterns:
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Lambda Functions – Run code in response to events or API calls without managing servers. You write a handler function, connect it to a trigger (API Gateway, Amazon S3, Amazon SQS, EventBridge, and 200+ other AWS services), and Lambda executes it. Each invocation runs independently with no shared state, scaling horizontally to match demand. Lambda manages execution environments, scaling, routing, and fault tolerance.
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Lambda MicroVMs – Isolated compute environments with near-instant startup and state retention for up to 8 hours. Designed for workloads needing a dedicated compute environment for each individual user or job. Lambda manages isolation, capacity, and networking. Your application uses Lambda MicroVMs APIs and HTTPS endpoints to connect each user/job to their compute environment.
For pricing information, see AWS Lambda Pricing
How Lambda Functions and Lambda MicroVMs compare
Lambda Functions and Lambda MicroVMs share a common serverless foundation:
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No server management – AWS manages underlying infrastructure, instance patching, and capacity.
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Pay-per-use billing – No upfront commitments. You pay only for the resources used.
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Managed networking – Both provide service-managed inbound and outbound network access.
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Firecracker virtualization – VM-level isolation between workloads.
While they share this foundation, they serve different use cases:
| Lambda Functions | Lambda MicroVMs | |
|---|---|---|
| Best for | Request-response or event-driven workloads (APIs, data processing, automation) | Persistent environments running user or AI-produced untrusted code |
| Programming model | Function handler invoked in a supported runtime | Any application – run your own binaries, listen on ports, use Linux OS capabilities |
| Duration | Up to 15 minutes per invocation; multi-step workflows lasting up to a year with Lambda Durable Functions | Up to 8 hours per session; suspend and resume across sessions |
| Runtime environment | Service-provided language runtimes; support for customer-provided runtimes | Customer-provided MicroVM images |
| Inbound Networking | Direct invocations or event-source integrations with AWS services; support for response streaming | Inbound access to any port using OSI Layer 7 protocols |
| Concurrency | One request per execution environment at a time | Multiple concurrent connections per MicroVM |
| Environment State | Execution environments may be reused (warm starts), but state may not persist across invocations | Memory and disk state preserved on suspend; restored on resume |
| Scaling | Automatic – Lambda creates and destroys execution environments in response to traffic | Developer-controlled – you create, suspend, resume, and terminate MicroVMs via API |
| Lifecycle | Fully managed by Lambda | Developer-controlled; optional idle policies for automatic suspend-resume |
| Pricing | Per-request + GB-seconds of execution time | Per-second of compute while running + snapshot storage while suspended |
