## TL;DR

The agent saw several near-identical CloudWatch alarms and deleted the "duplicates," but they were per-AZ copies by design: each watches its AZ's resources independently. Restore the deleted alarms, tag intentional copies with their scope, and require a design review (not just name similarity) before any alarm deletion. Similar names do not mean redundant purpose.

## Error

```text
agent deleted "duplicate" cloudwatch alarms  -  they were per-AZ copies by design
```

## Steps

1. Identify the deleted alarms and their per-AZ scope from the design or infrastructure code. Expected: the intentional copies are enumerated.
2. Recreate the deleted alarms with their original AZ-scoped dimensions. Expected: per-AZ coverage is restored.
3. Tag intentional alarm copies with their scope (e.g. az-specific monitoring). Expected: the design intent is machine-readable.
4. Change the deduplication logic: require identical dimensions and scope, not just similar names, before flagging duplicates. Expected: per-AZ copies are never flagged.
5. Require human approval for alarm deletions. Expected: no automated alarm removal without review.

## When to use

- Alarm cleanup deletes intentional copies.
- Alarms are scoped per AZ or per resource by design.
- Reviewing alarm deduplication logic.

## When not to use

- The alarms are truly duplicated (same dimensions, same scope).
- The alarms were meant to be decommissioned.
- The issue is alarm noise, not deletion.

## Tool compatibility

AWS CloudWatch alarms (current 2026 releases).

### Variant phrasings

### "duplicate" alarms were per-az by design

Compare dimensions and scope, not names.

### alarm cleanup removed az coverage

Restore the copies and tag their intent.

### dedup logic too aggressive on alarms

Require identical scope before calling it a duplicate.

## Why it happens

Monitoring designs often replicate alarms per AZ, per shard, or per replica for independent coverage; the names look duplicated because the pattern is systematic. Name-similarity deduplication mistakes the pattern for redundancy. True duplication means identical dimensions and thresholds serving the same scope; anything scoped differently is a distinct alarm wearing a similar name.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_FwmYeDfwN0JT6BWx2shyaw