# What is AWS Lambda?
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AWS Lambda is a compute service that runs code without the need to manage servers. Your code runs, scaling up and down automatically, with pay-per-use pricing. To get started, see [Create your first function](getting-started.md).

You can use Lambda for:
+ **File processing**: Process files automatically when uploaded to Amazon Simple Storage Service. See [file processing examples](example-apps.md#examples-apps-file) for details.
+ **Long-running workflows:** Use [durable Lambda functions](durable-functions.md) to build stateful, multi-step workflows that can run for up to one year. Perfect for order processing, approval workflows, human-in-the-loop processes, and complex data pipelines that need to remember their progress.
+ **Database operations and integration examples**: Respond to database changes and automate data workflows. See [database examples](example-apps.md#examples-apps-database) for details.
+ **Scheduled and periodic tasks**: Run automated operations on a regular schedule using EventBridge. See [scheduled task examples](example-apps.md#examples-apps-scheduled) for details.
+ **Stream processing**: Process real-time data streams for analytics and monitoring. See [Kinesis Data Streams](with-kinesis.md) for details.
+ **Web applications**: Build scalable web apps that automatically adjust to demand.
+ **Mobile backends**: Create secure API backends for mobile and web applications.
+ **IoT backends**: Handle web, mobile, IoT, and third-party API requests. See [IoT](services-iot.md) for details.

For pricing information, see [AWS Lambda Pricing](https://aws.amazon.com/lambda/pricing/).

## How Lambda works
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When using Lambda, you are responsible only for your code. Lambda runs your code on a high-availability compute infrastructure and manages all the computing resources, including server and operating system maintenance, capacity provisioning, automatic scaling, and logging.

Because Lambda is a serverless, event-driven compute service, it uses a different programming paradigm than traditional web applications. The following model illustrates how Lambda works:

1. You write and organize your code in [Lambda functions](concepts-basics.md#gettingstarted-concepts-function), which are the basic building blocks you use to create a Lambda application.

1. You control security and access through [Lambda permissions](lambda-permissions.md), using [execution roles](lambda-intro-execution-role.md) to manage what AWS services your functions can interact with and what resource policies can interact with your code.

1. Event sources and AWS services [trigger](concepts-event-driven-architectures.md) your Lambda functions, passing event data in JSON format, which your functions process (this includes event source mappings).

1. [Lambda runs your code](concepts-how-lambda-runs-code.md) with language-specific runtimes (like Node.js and Python) in execution environments that package your runtime, layers, and extensions.

**Tip**  
To learn how to build **serverless solutions**, check out the [Serverless Developer Guide](https://docs.aws.amazon.com/serverless/latest/devguide/).

## Key features
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**Configure, control, and deploy secure applications:**
+ [Environment variables](configuration-envvars.md) modify application behavior without new code deployments.
+ [Versions](configuration-versions.md) safely test new features while maintaining stable production environments.
+ [Lambda layers](chapter-layers.md) optimize code reuse and maintenance by sharing common components across multiple functions.
+ [Code signing](configuration-codesigning.md) enforce security compliance by ensuring only approved code reaches production systems.

**Scale and perform reliably:**
+ [Concurrency and scaling controls](lambda-concurrency.md) precisely manage application responsiveness and resource utilization during traffic spikes.
+ [Lambda SnapStart](snapstart.md) significantly reduce cold start times. Lambda SnapStart can provide as low as sub-second startup performance, typically with no changes to your function code.
+ [Response streaming](configuration-response-streaming.md) optimize function performance by delivering large payloads incrementally for real-time processing.
+ [Container images](images-create.md) package functions with complex dependencies using container workflows.

**Connect and integrate seamlessly:**
+ [VPC networks](configuration-vpc.md) secure sensitive resources and internal services.
+ [File systems](configuration-filesystem.md) integration that shares persistent data and manage stateful operations across function invocations.
+ [Function URLs](urls-configuration.md) create public-facing APIs and endpoints without additional services.
+ [Lambda extensions](lambda-extensions.md) augment functions with monitoring, security, and operational tools.

## Related information
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+ For information on how Lambda works, see [How Lambda works](concepts-basics.md).
+ To start using Lambda, see [Create your first Lambda function](getting-started.md). 
+ For a list of example applications, see [Getting started with example applications and patterns](example-apps.md).