{
  "slug": "cargo-lambda-watch-processes-concurrent-invocations-9c1c41b88c7f",
  "title": "cargo-lambda watch processes concurrent invocations",
  "tools": [
    "cargo-lambda"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-02-15T19:11:15.000Z",
  "announced_at": "2026-02-15T19:11:15.000Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "When you need local Lambda requests processed simultaneously, run `cargo lambda watch --concurrency 5` to allow up to five function instances, spawned on demand. Instances poll a shared queue, remain warm, and each runs with `AWS_LAMBDA_MAX_CONCURRENCY=1`; the limit is global per function.",
    "examples": [
      "cargo lambda watch --concurrency 5"
    ],
    "gotchas": [
      "Version: v1.9.0",
      "--concurrency <maximum instances>: Sets the maximum number of function instances; instances are spawned dynamically based on demand. The documentation example uses `5`.",
      "Prerequisite: Run `cargo lambda watch` at the root of a Rust workspace.",
      "Concurrency is limited globally per function.",
      "Each instance runs in single-worker mode with `AWS_LAMBDA_MAX_CONCURRENCY=1`."
    ]
  },
  "why_it_matters": "Run a local Lambda function with multiple requests handled simultaneously.",
  "before": "By default, `cargo lambda watch` processes Lambda invocations sequentially with a single function instance.",
  "sources": [
    "https://github.com/cargo-lambda/cargo-lambda/releases/tag/v1.9.0",
    "https://github.com/cargo-lambda/cargo-lambda/pull/921",
    "https://github.com/cargo-lambda/cargo-lambda/blob/v1.9.0/docs/commands/watch.md"
  ],
  "rank": 0.98023,
  "judge": {
    "publish": true,
    "judge_model": "codex-cli/gpt-6-luna+typesafe/jev-1.13.0",
    "prompt_version": "extract-v7+enrich-v2+judge-v2x3+jev-publish-v1"
  },
  "review_state": "approved",
  "provenance": {
    "run_id": "wave1b-tools-20261017",
    "verdict_id": "wave1b-tools-20261017:wave1b-tools-20261017-755fa2cb01364297-12:gate",
    "evidence_hash": "aa219556fc6395aa6acfa392dbfa7af6b7cb3cfcb85a92922d99c616f256163a"
  },
  "review": {
    "draft_hash": "5654e2ce73876f82a9ad4f11d10b6d4b5d5ae77bdf5b6f0fdfb2aebfcf9feed2",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-07T00:00:00.000Z",
    "decision": "wave1b-tools-20261017:gate",
    "reason": "3 of 3 judge runs approved with p_yes >= 0.9 (mean 0.98 >= 0.9; 2 needed) and Jev gave 0.76 (>= 0.6 needed)."
  }
}