If Users follow records, the entries are stored in EntitySubscription entity.
SOQL:
SELECT Id, ParentId, SubscriberId
FROM EntitySubscription
SubscriberId – ID of the User who is following the record or user.
ParentId – ID of the record or user which the user is following.
Sample SOQL:
SELECT Id, ParentId, SubscriberId
FROM EntitySubscription
WHERE ParentId = '5008c00001JLPRIAA5'