Anyone know why firebase storage would be so ridiculously slow compared to firebase hosting?
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I found the solution.
If you have your files already uploaded to storage go to: https://console.cloud.google.com/storage/browser?project=your_project > pick your bucket > select all interesting files and click Make public (or something similar - I'm not english native).
To have all new uploaded files public by default you need to install Google cloud SDK (https://cloud.google.com/sdk/docs/) and from your command line use the following command for your bucket:
gsutil defacl set public-read gs://your_bucket
After that all my current and new images are available here storage.googleapis.com/my_project.appspot.com/img/image_name.jpg and downloading time is definitely shorter.