### Requirement
* To analyze the relation between email accounts and one device

### Database Schema

|| device_uid <br><span style="color:red">(partition key)</span> | email_hash_identifier <br><span style="color:red">(sort key)</span> | email_type | is_new_device |creation_time |
|---| --------- | ---------- | --- | --- |--- |
|type| string | string | number | bool | number |
|example|d1|e1#2019-07-22|0|True|1564466925|

device_checkin_table.query(KeyConditionExpression=Key('device_uid').eq(device_uid) & Key('email_hash_identifier').begins_with(email_hash),
                                       ScanIndexForward=False,
                                       Limit=1)