# System log event schema for Lambda Web Functions
Lambda writes the following system events to your Web Function's log group. Each event is a JSON object with the envelope fields described in [Event envelope](#web-functions-logging-system-log-schema-envelope) and a `record` object whose fields depend on the event type. The level of each event determines whether Lambda delivers it. For more information, see [System logs](web-functions-logging.md#web-functions-logging-system-logs).
| Event type | Record object | Description |
| --- | --- | --- |
| platform.initStart | PlatformInitStart | Environment initialization started. |
| platform.initReport | PlatformInitReport | Report of environment initialization, whether it succeeded or failed. |
| platform.invokeStart | PlatformInvokeStart | The environment started serving requests. |
| platform.requestComplete | PlatformRequestComplete | One HTTP request completed. Logged at DEBUG only. |
| platform.invokeSummary | PlatformInvokeSummary | Summary of the environment's activity, emitted about every 60 seconds. |
| platform.invokeReport | PlatformInvokeReport | Report of the environment's whole serving period, emitted when it stops serving. |
| platform.spinDownStart | PlatformSpinDownStart | Environment shutdown started. |
| platform.spinDownReport | PlatformSpinDownReport | Report of environment shutdown. |
| platform.logsDropped | PlatformLogsDropped | Log records were dropped because logs were produced faster than they could be delivered. |
In the field lists on this page, a question mark (`?`) after a field name means that the field might not be present. Types that are not JSON types, such as `InitType`, `Status`, or `InvokeSummaryMetrics`, are defined in [Shared object types](#web-functions-logging-system-log-schema-types), and each one links to its definition.
## `platform.initStart`
The environment initialization phase started.
Level: `INFO`
The `record` object has the following fields:
+ `functionName` (`String`) – The name of the function.
+ `revisionId` (`String`) – The revision that the environment runs.
+ `instanceId` (`String`) – The identifier of the execution environment.
+ `initializationType` ([`InitType`](#web-functions-logging-system-log-schema-inittype)) – How Lambda initialized the environment.
+ `runtimeVersion` (`String`) – The runtime version that the environment runs.
+ `runtimeVersionArn` (`String`) – The Amazon Resource Name (ARN) of the runtime version.
```
{
"timestamp": "2026-09-25T11:12:30.893Z",
"level": "INFO",
"type": "platform.initStart",
"region": "us-east-1",
"record": {
"runtimeVersion": "nodejs24.x:nodejs.web24.v51",
"runtimeVersionArn": "arn:aws:lambda:us-east-1::runtime/nodejs24.x/version/nodejs.web24.v51",
"functionName": "my-web-app",
"revisionId": "rev-fs0fq",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45",
"initializationType": "native-http"
}
}
```
## `platform.initReport`
Overall report of the initialization phase.
Level: `INFO` when status is success, `WARN` when failure.
The `record` object has the following fields:
+ `status` ([`Status`](#web-functions-logging-system-log-schema-status)) – The outcome of the initialization phase.
+ `errorType?` (`String`) – Present when status is failure. Values such as `Runtime.ImportCodeError`, `Application.InitCodeError`, and `Runtime.InitTimeout`.
+ `initializationType` ([`InitType`](#web-functions-logging-system-log-schema-inittype)) – How Lambda initialized the environment.
+ `metrics` ([`InitReportMetrics`](#web-functions-logging-system-log-schema-initreportmetrics)) – Metrics for the initialization phase.
Success example:
```
{
"timestamp": "2026-09-25T11:12:31.143Z",
"level": "INFO",
"type": "platform.initReport",
"region": "us-east-1",
"record": {
"status": "success",
"initializationType": "native-http",
"metrics": {
"totalDurationMs": 304.000,
"totalCpuTimeMs": 143.000,
"maxMemoryUsageMb": 142
}
}
}
```
Failure example, where the handler module failed to load:
```
{
"timestamp": "2026-09-25T11:16:04.164Z",
"level": "WARN",
"type": "platform.initReport",
"region": "us-east-1",
"record": {
"status": "failure",
"errorType": "Runtime.ImportCodeError",
"initializationType": "native-http",
"metrics": {
"totalDurationMs": 320.000,
"totalCpuTimeMs": 137.000,
"maxMemoryUsageMb": 138
}
}
}
```
## `platform.invokeStart`
The environment finished initializing and started serving requests. Lambda emits this event once per environment, not once per request, and only when initialization succeeded.
Level: `INFO`
The `record` object has the following fields:
+ `functionName` (`String`) – The name of the function.
+ `revisionId` (`String`) – The revision that the environment runs.
+ `instanceId` (`String`) – The identifier of the execution environment.
```
{
"timestamp": "2026-09-25T11:12:31.144Z",
"level": "INFO",
"type": "platform.invokeStart",
"region": "us-east-1",
"record": {
"functionName": "my-web-app",
"revisionId": "rev-fs0fq",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45"
}
}
```
## `platform.requestComplete`
One HTTP request finished, successfully or not.
Level: `DEBUG`, so Lambda delivers it only when `systemLogLevel` is `DEBUG`.
The `record` object has the following fields:
+ `requestId` (`String`) – The request ID.
+ `endpointName` (`String`) – The endpoint that served the request.
+ `result` (`Integer`) – The HTTP status code returned to the client.
+ `errorType?` (`String`) – Present when Lambda failed the request. Values such as `Runtime.RequestTimeout` and `Platform.InvalidRequest`.
+ `metrics` ([`RequestCompleteMetrics`](#web-functions-logging-system-log-schema-requestcompletemetrics)) – Metrics for the request.
Success example:
```
{
"timestamp": "2026-09-25T11:12:31.154Z",
"level": "DEBUG",
"type": "platform.requestComplete",
"region": "us-east-1",
"record": {
"requestId": "KXH25FBDZ33GP4TQ4ARAUYSTSA",
"endpointName": "default",
"result": 200,
"metrics": {
"durationMs": 4.484,
"responseBytes": 40
}
}
}
```
Timeout example:
```
{
"timestamp": "2026-09-25T11:12:34.926Z",
"level": "DEBUG",
"type": "platform.requestComplete",
"region": "us-east-1",
"record": {
"requestId": "5SXHGVX2GD64ND6NQVEBAY235Q",
"endpointName": "default",
"result": 504,
"errorType": "Runtime.RequestTimeout",
"metrics": {
"durationMs": 3001.229,
"responseBytes": 0
}
}
}
```
## `platform.invokeSummary`
Summarizes one window of about 60 seconds of an environment's activity. Lambda emits it for every live environment, including idle windows where `requests` is 0.
Level: `INFO`
The `record` object has the following fields:
+ `startTime` (`String`) – The start of the summary window (RFC 3339).
+ `instanceId` (`String`) – The identifier of the execution environment.
+ `metrics` ([`InvokeSummaryMetrics`](#web-functions-logging-system-log-schema-invokesummarymetrics)) – Metrics for the window.
```
{
"timestamp": "2026-09-25T11:13:31.143Z",
"level": "INFO",
"type": "platform.invokeSummary",
"region": "us-east-1",
"record": {
"startTime": "2026-09-25T11:12:31.144547426Z",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45",
"metrics": {
"requests": 4,
"concurrentRequests": 1,
"cpuTimeMs": 420.000,
"maxMemoryUsageMb": 154
}
}
}
```
## `platform.invokeReport`
Overall report of the environment's serving period, from invokeStart until it stops serving. Lambda emits it once per environment, at shutdown.
Level: `INFO` when status is success, `WARN` when failure.
The `record` object has the following fields:
+ `status` ([`Status`](#web-functions-logging-system-log-schema-status)) – The outcome of the serving period.
+ `errorType?` (`String`) – Present when status is failure. Values such as `Runtime.Exit`, `Runtime.ExitError`, and `Runtime.OutOfMemory`.
+ `instanceId` (`String`) – The identifier of the execution environment.
+ `metrics` ([`InvokeReportMetrics`](#web-functions-logging-system-log-schema-invokereportmetrics)) – Metrics for the serving period.
A request timeout does not fail the serving period. The `status` stays `success`.
Success example:
```
{
"timestamp": "2026-09-25T11:19:11.858Z",
"level": "INFO",
"type": "platform.invokeReport",
"region": "us-east-1",
"record": {
"status": "success",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45",
"metrics": {
"totalCpuTimeMs": 973.000,
"totalDurationMs": 400723.000,
"totalRequests": 4,
"concurrentRequests": 1,
"maxMemoryUsageMb": 157
}
}
}
```
Failure example:
```
{
"timestamp": "2026-09-25T11:19:11.858Z",
"level": "WARN",
"type": "platform.invokeReport",
"region": "us-east-1",
"record": {
"status": "failure",
"errorType": "Runtime.OutOfMemory",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45",
"metrics": {
"totalCpuTimeMs": 973.000,
"totalDurationMs": 400723.000,
"totalRequests": 4,
"concurrentRequests": 1,
"maxMemoryUsageMb": 512
}
}
}
```
## `platform.spinDownStart`
Environment shutdown started.
Level: `INFO`
The `record` object has the following fields:
+ `functionName` (`String`) – The name of the function.
+ `revisionId` (`String`) – The revision that the environment runs.
+ `instanceId` (`String`) – The identifier of the execution environment.
```
{
"timestamp": "2026-09-25T11:19:11.858Z",
"level": "INFO",
"type": "platform.spinDownStart",
"region": "us-east-1",
"record": {
"functionName": "my-web-app",
"revisionId": "rev-fs0fq",
"instanceId": "52754708-44f1-407a-a1fd-6d2a98175a45"
}
}
```
## `platform.spinDownReport`
Overall report of the shutdown.
Lambda sends `SIGTERM` to your application and waits up to 1 second for it to exit. If the application is still running, Lambda stops it with `SIGKILL` and reports a failure with the error type `Runtime.SpinDownTimeout`.
Level: `INFO` when status is success, `WARN` when failure.
The `record` object has the following fields:
+ `status` ([`Status`](#web-functions-logging-system-log-schema-status)) – The outcome of the shutdown phase.
+ `errorType?` (`String`) – Present when status is failure. Values such as `Runtime.SpinDownTimeout` and `Runtime.ExitError`.
+ `metrics` ([`SpinDownReportMetrics`](#web-functions-logging-system-log-schema-spindownreportmetrics)) – Metrics for the shutdown phase.
Success example:
```
{
"timestamp": "2026-09-25T11:19:11.879Z",
"level": "INFO",
"type": "platform.spinDownReport",
"region": "us-east-1",
"record": {
"status": "success",
"metrics": {
"totalDurationMs": 21.000,
"totalCpuTimeMs": 8.000,
"maxMemoryUsageMb": 157
}
}
}
```
Failure example:
```
{
"timestamp": "2026-09-25T11:19:12.879Z",
"level": "WARN",
"type": "platform.spinDownReport",
"region": "us-east-1",
"record": {
"status": "failure",
"errorType": "Runtime.SpinDownTimeout",
"metrics": {
"totalDurationMs": 1021.000,
"totalCpuTimeMs": 8.000,
"maxMemoryUsageMb": 157
}
}
}
```
## `platform.logsDropped`
Log records were dropped because logs were produced faster than they could be delivered.
Level: `WARN`
The `record` object has the following fields:
+ `reason` (`String`) – Why the records were dropped.
+ `droppedRecords` (`Integer`) – Records dropped since the last record that was delivered.
+ `droppedBytes` (`Integer`) – Bytes dropped since the last record that was delivered.
Both counts accumulate across consecutive drops and reset to 0 after a record is delivered.
```
{
"timestamp": "2026-09-25T11:20:00.000Z",
"level": "WARN",
"type": "platform.logsDropped",
"region": "us-east-1",
"record": {
"reason": "Some logs were dropped because the downstream consumer is slower than the logs production rate",
"droppedRecords": 120,
"droppedBytes": 48000
}
}
```
## Shared object types
The following types appear in the field lists of the events on this page.
### Event envelope
Every system event has the following envelope fields:
+ `timestamp` (`String`) – RFC 3339 in UTC.
+ `level` (`Level`) – The level of the event.
+ `type` (`String`) – The event type (`platform.*`).
+ `region` (`String`) – The Region where the execution environment ran.
+ `record` (`Object`) – The event-specific fields.
### `InitType`
String enum that describes how Lambda initialized the environment. Web Functions always use `native-http`.
### `Level`
String enum for the level of a system event: `DEBUG`, `INFO`, or `WARN`. System events are never `ERROR` or `FATAL`. Report events are `INFO` when status is success and `WARN` when it is failure.
### `Status`
String enum that describes the outcome of a phase: `success` or `failure`. When it is `failure`, the record also contains `errorType`.
### `InitReportMetrics`
+ `totalDurationMs` (`Double`) – Wall-clock time of the initialization phase.
+ `totalCpuTimeMs` (`Double`) – CPU time consumed during initialization.
+ `maxMemoryUsageMb` (`Integer`) – Peak memory of the environment, in MiB.
### `RequestCompleteMetrics`
+ `durationMs` (`Double`) – Wall-clock time of the request.
+ `responseBytes` (`Integer`) – Response body bytes sent.
### `InvokeSummaryMetrics`
+ `requests` (`Integer`) – Requests completed in the window.
+ `concurrentRequests` (`Integer`) – Maximum concurrent requests in the window.
+ `cpuTimeMs` (`Double`) – CPU time consumed in the window.
+ `maxMemoryUsageMb` (`Integer`) – Peak memory of the environment, in MiB.
### `InvokeReportMetrics`
+ `totalCpuTimeMs` (`Double`) – CPU time over the serving period.
+ `totalDurationMs` (`Double`) – Wall-clock time from invokeStart until the environment stopped serving.
+ `totalRequests` (`Integer`) – Total requests served.
+ `concurrentRequests` (`Integer`) – Maximum concurrent requests over the period.
+ `maxMemoryUsageMb` (`Integer`) – Peak memory of the environment, in MiB.
### `SpinDownReportMetrics`
+ `totalDurationMs` (`Double`) – Wall-clock time of the shutdown phase.
+ `totalCpuTimeMs` (`Double`) – CPU time consumed during shutdown.
+ `maxMemoryUsageMb` (`Integer`) – Peak memory of the environment, in MiB.