Sharing Images Via Webhook

[njordan]

TL:DR Are images stored in Drive and Google Photos? Signed image URLs have a Google Photos prefix (lh3.googleusercontent.com/...)

The question I'm trying to answer with this exploration is: where are all the locations my AppSheet images are stored with default configuration on a Core plan with Sheets as a data source? Existing documentation says my images are only in a Drive folder in the same directory as my Sheet but that doesn't seem like a complete answer, see below.

I'm pushing data from an image column to a 3rd party API using a webhook automation. I wanted to confirm that the 3rd party app was storing it's own copy of the image, not just referencing a URL to the AppSheet image stored in Drive, so I deleted the image in Drive and went to see if the image was still available over in my 3rd party app. If the app was just referencing a URL, the image wouldn't be accessible right? I deleted the Drive image and confirmed the image was still available in the 3rd party app, so far so good. Then I noticed that the deleted image still showed in my AppSheet app too even after syncing/refreshing. Why would that be? 

Seems like images must be stored and referenced from somewhere other than the default Drive folder. My second piece of evidence is, the webhook json payload for my image is a signed Google Photos URL (real example, no PII):

https://lh3.googleusercontent.com/5QMa1FDFRDo7nNbBMFKvLkDcC7w7nE6tkNu3Rhbrv2tKW07oKUbNVYYdbOl-JIV0=w....

Why this matters: I need to have a precise understanding of where the 'master' record for my images are so I can build robust downstream customer visible applications. Also I'm curious.

[Steve]

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Are images stored in Drive and Google Photos?

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No.

[njordan]

That would certainly simplify things. Any clue as to why a deleted image file still shows up in my app and is still available at the signed URL produced by the webhook?

[Steve · Accepted solution]

AppSheet uses server-side caching extensively. The image stays in cache regardless of what you do to it in the app or at the data source. The cache expires eventually, but Google hasn't disclosed what the expiration period is. The app creator has no control over the cache.