# Using sentinel for monitoring TVL

**URL:** <https://forum.openzeppelin.com/t/using-sentinel-for-monitoring-tvl/37545>\
**Category:** Defender\
**Tags:** sentinel\
**Created:** [August 21, 2023, 4:23am UTC](https://forum.openzeppelin.com/t/using-sentinel-for-monitoring-tvl/37545 "2023-08-21T04:23:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Zartaj](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/zartaj/32/19230_2.png) [@Zartaj](https://forum.openzeppelin.com/u/Zartaj)\
**Post date:** [August 21, 2023, 4:23am UTC](https://forum.openzeppelin.com/t/using-sentinel-for-monitoring-tvl/37545/1 "2023-08-21T04:23:39Z")

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I have two questions for sentinel.

1. Is there any way to monitor any sudden drop in the TVL. In my case the TVL we will monitor is an ERC20 token. Any kind of sudden drop in the tokens inside the contract should alert.

2. As we can already monitor transfer events, but this limits us to get alerts for only one transaction, but what if we monitor a certain amount of let's say 10k tokens being transferred within 30 minutes. That means their are 10,20,30, etc. transactions with a combined value of 10k tokens within 30 minutes, is it somehow achievable.

I know this is too much out of the box, but may be there's something similar available.

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<div class="post-metadata">

**Author:** ![emnul](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/emnul/32/18922_2.png) [@emnul](https://forum.openzeppelin.com/u/emnul)\
**Post date:** [August 21, 2023, 3:19pm UTC](https://forum.openzeppelin.com/t/using-sentinel-for-monitoring-tvl/37545/2 "2023-08-21T15:19:32Z")

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[Forta Sentinels](https://docs.openzeppelin.com/defender/sentinel#whats-in-a-forta-sentinel) are excellent tools for these use cases. We have an [ERC-20 balance monitoring example](https://docs.openzeppelin.com/defender/guide-balance-automation-forta-sentinel) in our docs that you could modify to meet your needs.