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DOC-303: Document concurrent SQS event source mapping pollers #810

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DOC-303: Document concurrent SQS event source mapping pollers #810

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1 change: 1 addition & 0 deletions src/content/docs/aws/customization/configuration-options.md
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Expand Up @@ -273,6 +273,7 @@ Please consult the [migration guide](/aws/services/lambda#migrating-to-lambda-v2
| `LAMBDA_DOCKER_FLAGS` | `-e KEY=VALUE`, `-v host:container`, `-p host:container`, `--add-host domain:ip` | Additional flags passed to Docker `run`\|`create` commands. Supports environment variables (also with `--env-file`, but the file has to be mounted into the LocalStack container), ports, volume mounts, extra hosts, networks, DNS servers, labels, ulimits, user, platform, and privileged mode. The `--env-file` argument for Docker `run` and Docker Compose have different feature sets. To provide both, we support the `--env-file` for environment files with the docker run syntax, while `--compose-env-file` supports the full docker compose features, like placeholders with `${}`, replacing quotes, etc. |
| `LAMBDA_DOCKER_NETWORK` | `bridge` (Docker default) | [Docker network driver](https://docs.docker.com/network/) for the Lambda and ECS containers. Needs to be set to the network the LocalStack container is connected to. Limitation: `host` mode currently not supported. |
| `LAMBDA_DOWNLOAD_AWS_LAYERS` | `1` (default, pro) | Whether to download public Lambda layers from AWS through a LocalStack proxy when creating or updating functions. |
| `LAMBDA_EVENT_SOURCE_MAPPING_SQS_POLLER_COUNT` | `5` (default) | Number of concurrent pollers spawned per SQS event source mapping for standard queues, each running in its own thread. Capped by `ScalingConfig.MaximumConcurrency` when set on the event source mapping. FIFO queues always use a single poller to preserve message-group ordering. |
| `LAMBDA_IGNORE_ARCHITECTURE` | `0` (default) | Whether to ignore the AWS architectures (x86_64 or arm64) configured for the lambda function. Set to `1` to run cross-platform compatible lambda functions natively (i.e., Docker selects architecture). |
| `LAMBDA_K8S_IMAGE_PREFIX` | `amazon/aws-lambda-` (default, enterprise) | Prefix for images that will be used to execute Lambda functions in Kubernetes. |
| `LAMBDA_K8S_INIT_IMAGE` | | Specify the image for downloading the init binary from LocalStack. The image must include the `curl` and `chmod` commands. This is only relevant for container-based Lambdas on Kubernetes |
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4 changes: 2 additions & 2 deletions src/content/docs/aws/services/lambda.mdx
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Expand Up @@ -306,7 +306,7 @@ import { Table, TableHeader, TableBody, TableHead, TableRow, TableCell } from '@
<TableRow>
<TableCell className="font-medium">ScalingConfig</TableCell>
<TableCell>The scaling configuration for the event source. [^3]</TableCell>
<TableCell className="text-center">🟡</TableCell>
<TableCell className="text-center">🟢</TableCell>
<TableCell className="text-center">🟡</TableCell>
<TableCell className="text-center">➖</TableCell>
<TableCell className="text-center">➖</TableCell>
Expand Down Expand Up @@ -428,7 +428,7 @@ import { Table, TableHeader, TableBody, TableHead, TableRow, TableCell } from '@

[^1]: Read more at [Control which events Lambda sends to your function](https://docs.aws.amazon.com/lambda/latest/dg/invocation-eventfiltering.html)
[^2]: The available Metadata properties may not have full parity with AWS depending on the event source (read more at [Understanding event filtering basics](https://docs.aws.amazon.com/lambda/latest/dg/invocation-eventfiltering.html#filtering-basics)).
[^3]: For SQS Standard, `ScalingConfig` is accepted but not automatically applied — the poller count is currently hard-coded rather than scaled based on `MaximumConcurrency`. For SQS FIFO, a single poller is always used to preserve message-group ordering, so the scaling configuration is accepted but has no effect.
[^3]: For SQS Standard, LocalStack spawns multiple concurrent pollers per event source mapping (`LAMBDA_EVENT_SOURCE_MAPPING_SQS_POLLER_COUNT`, default `5`), and `ScalingConfig.MaximumConcurrency` caps the poller count when set. For SQS FIFO, a single poller is always used to preserve message-group ordering, so the scaling configuration is accepted but has no effect.
[^4]: For SQS Standard, only `MinimumPollers` is honored (it sets the poller count); `MaximumPollers` has no effect. For SQS FIFO, the single-poller model means the configuration is accepted but ignored.

Create a [GitHub Discussion](https://github.com/orgs/localstack/discussions/new/choose) or reach out to [LocalStack Support](/aws/help-support/get-help/) if you experience any challenges.
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