# Deep Dive: AWS Lambda Functions

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This page is a deep dive into configuring the SeaLights Go Agent for AWS Lambda Functions. For more direct instructions, visit [#using-the-sealights-go-agent-with-a-lambda-function](https://docs.sealights.io/knowledgebase/setup-and-configuration/sealights-agents-and-plugins/go-agent/go-agent-v2/go-agent-how-to-use/coverage-listener-mode-application-under-test/..#using-the-sealights-go-agent-with-a-lambda-function "mention")
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## Go Agent Configuration for AWS Lambda Functions

AWS Lambda functions have unique performance and network constraints that require specialized agent configuration. The SeaLights Go Agent provides **Light Mode** specifically designed for Lambda environments.

### Why Light Mode is Required for Lambda

Lambda functions must start quickly and minimize resource usage. The standard SeaLights agent includes background processes that are incompatible with Lambda's execution model:

* **Cold Start Impact**: Background processes increase Lambda initialization time
* **Memory Constraints**: Multiple agent threads consume precious Lambda memory allocation
* **Network Efficiency**: Lambda benefits from optimized network routing via collectors
* **Execution Model**: Lambda's stateless nature doesn't require persistent agent connections

### What Light Mode Does

Light Mode transforms the agent into a lightweight coverage collector by:

**Processes Disabled:**

* Agent heartbeat communication
* Remote configuration retrieval
* Log submission to SeaLights backend
* Idle mode notifications
* Test event processing (footprints only)

**Optimizations Enabled:**

* Preferential use of collector URLs for network efficiency
* Special agent mode headers for backend optimization
* Simplified footprint reporting without execution ID requirements
* Reduced memory footprint and CPU usage

### Required Configuration

**Environment Variables (Set in Lambda Configuration):**

```bash
SL_LIGHT_MODE=true
SL_COLLECTOR_URL=<your-collector-endpoint>
```

**Why Runtime Configuration:** These parameters should be set as Lambda environment variables, not during the build-time `config`/`instrument` steps. Setting `SL_LIGHT_MODE=true` during build configuration can interfere with unit test coverage collection during development.

### Technical Implementation Details

When Light Mode is enabled, the agent:

1. **Simplified Startup**: Skips standard agent initialization processes
2. **Footprint Only**: Processes lightweight coverage footprints
3. **Collector Priority**: Routes all traffic through collector URLs (as configured with `SL_COLLECTOR_URL`

### Performance Benefits

**Cold Start Optimization:**

* Eliminates background goroutines that delay Lambda initialization
* Reduces memory allocation during startup
* Minimizes network connections during function bootstrap

**Runtime Efficiency:**

* Lower CPU usage through simplified processing
* Reduced memory footprint
* Optimized network routing through collector infrastructure
* No persistent connections or heartbeat overhead

### Deployment Examples

**Lambda Environment Variables:**

```bash
SL_LIGHT_MODE=true
SL_COLLECTOR_URL=https://your-collector.example.com
SL_TOKEN=your-sealights-token
SL_LAB_ID=lambda-production-environment
```

**Terraform Configuration:**

```hcl
resource "aws_lambda_function" "instrumented_function" {
  # ... other configuration
  
  environment {
    variables = {
      SL_LIGHT_MODE     = "true"
      SL_COLLECTOR_URL  = var.sealights_collector_url
      SL_TOKEN          = var.sealights_token
      SL_LAB_ID         = "lambda-${var.environment}"
    }
  }
}
```

### Important Limitations

**Use Only for Lambda**: Light Mode should exclusively be used for Lambda functions. It disables agent features that are beneficial for long-running applications and test runners.

**Coverage Collection**: Light Mode is designed for Coverage Listener Mode only. It cannot be used effectively in Test Runner Mode.

**Feature Restrictions**: Remote configuration, agent statistics, and real-time monitoring features are unavailable in Light Mode.

### Collector Configuration

For collector setup and configuration details, refer to the SeaLights Collector Documentation.

The collector provides:

* Reduced network latency for Lambda functions
* Optimized data routing to SeaLights backend
* Regional deployment options for compliance requirements