lastfm-scrobble-cleaner

Automatically detect and remove duplicate Last.fm scrobbles caused by apps replaying the last session on startup, deployed as an AWS Lambda on a daily schedule.

How It Works

EventBridge (daily cron)
  → Lambda
    → Last.fm API: fetch recent scrobbles
    → Detect duplicates (session replay + duration overlap)
    → Last.fm Web: delete flagged scrobbles via form POST
    → CloudWatch: log results

Detection uses two complementary methods:

• Session replay detection — if the first track of a new listening session matches the last track of the previous session, it's likely a resume/sync replay (common with Qobuz's cross-device sync and autoplay)
• Playback duration check — if the same track appears twice closer together than its actual duration, it wasn't really listened to (e.g., skipping through songs)

Deletion uses Last.fm's web form endpoint (POST /user/{username}/library/delete with CSRF token), since the library.removeScrobble API method is dead. No headless browser needed — just HTTP requests with session cookies.

Usage

Test deletion locally

cp .env.example .env
# Fill in LASTFM_API_KEY, LASTFM_API_SECRET, LASTFM_USERNAME, LASTFM_PASSWORD
npm install
npm run test-delete

Deploy to AWS

npm run bundle                          # build Lambda zip
cd infra && terraform init && terraform apply

After first deploy, populate the Secrets Manager secret with your Last.fm credentials. The Lambda runs daily at 02:00 UTC in dry-run mode by default — it logs what it would delete without actually deleting. Set DRY_RUN=false in the Lambda environment after validating the logs.

Configuration

Environment Variable	Default	Description
LASTFM_USERNAME	—	Last.fm username
LASTFM_API_KEY	—	API key from https://www.last.fm/api/account/create
LASTFM_API_SECRET	—	API shared secret
LASTFM_PASSWORD	—	Last.fm password (for web session auth)
DRY_RUN	true	Set to false to enable live deletions
SESSION_GAP_SECONDS	1800	Gap (seconds) that defines a new listening session
FETCH_WINDOW_HOURS	26	Hours of history to fetch (26h to catch boundary cases)
MAX_DELETIONS_PER_RUN	20	Circuit breaker — max deletions per run
DELETION_DELAY_MS	200	Base delay between deletion calls

Development

Setup

Requires Node.js >= 22 and Terraform >= 1.5.

git clone <repo-url> && cd lastfm-scrobble-cleaner
npm install
npx tsc --noEmit       # type check
npm run bundle         # build Lambda zip

Structure

src/
  lastfm-client.ts      # Last.fm API client (read-only: scrobbles, track info)
  lastfm-web.ts          # Web session login + form-based scrobble deletion
  detect-duplicates.ts   # Session replay + duration overlap detection
  duration-cache.ts      # In-memory + DynamoDB track duration cache
  config.ts              # Environment variable loading + defaults
  handler.ts             # Lambda entry point
  test-delete.ts         # Interactive test script for deletion
infra/
  main.tf                # Terraform — Lambda, EventBridge, DynamoDB, Secrets Manager, SNS

Infrastructure

Managed with Terraform (infra/main.tf):

• Lambda (Node.js 22, ARM64) — triggered daily by EventBridge
• DynamoDB — caches track durations to reduce API calls
• Secrets Manager — stores Last.fm credentials
• CloudWatch + SNS — error alarms