Serverless Developer Guide
After the handler ﬁnishes processing the ﬁrst event, the runtime sends it another, and another. 
Each instance of your function could process thousands of requests.
Unlike traditional servers, Lambda functions do not run constantly. When a function is triggered by 
an event, this is called an invocation. Lambda functions are limited to 15 minutes in duration, but 
on average, across all AWS customers, most invocations last for less than a second.
There are many types of invocation events. Some examples:
• HTTP request from API Gateway
• Schedule managed by an EventBridge rule
• Message from an IOT device
• Notiﬁcation that a ﬁle was uploaded to an S3 bucket
Even the smallest Lambda-based application uses at least one event that invokes your function.
How Lambda invokes your function (runtime environment)
Lambda invokes your function in an execution environment, which contains a secure and isolated
runtime environment.
• A runtime provides a language-speciﬁc environment which relays invocation events, context 
information, and responses between the Lambda and your functions.
• An execution environment manages the processes and resources that are required to run the 
function.
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