# Deriving FA token balance\_updates from big\_map\_diff

**URL:** https://forum.tezosagora.org/t/deriving-fa-token-balance-updates-from-big-map-diff/1972
**Category:** Research and Development
**Tags:** metadata, tokens, indexers, michelson
**Created:** [June 1, 2020, 12:41pm UTC](https://forum.tezosagora.org/t/deriving-fa-token-balance-updates-from-big-map-diff/1972 "2020-06-01T12:41:09Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![murbard](https://forum.tezosagora.org/user_avatar/forum.tezosagora.org/murbard/32/67_2.png) [@murbard](https://forum.tezosagora.org/u/murbard)
#### Post date: [June 1, 2020, 1:48pm UTC](https://forum.tezosagora.org/t/deriving-fa-token-balance-updates-from-big-map-diff/1972/2 "2020-06-01T13:48:21Z")

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For what it’s worth, I have real code for a real use case where some balances depend on a big map but also the current timestamp (e.g. some decay continuously over time, some accrue). You wouldn’t be able to infer balances just from a structure

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