Mailchimp CRON causing heavy load on DB

[jdereus87]

Magento 2.3.6
Mailchimp: 102.3.53

We are experiencing an issue in which the cronjob ebizmarts_ecommerce keeps running. It causes a high strain on the indexer (keeps adding records to the index backlog). The strain on the indexer causes a high CPU load and a slowly increasing memory usage.
We are looking to solve this problem,but are unsure of which path to take. Mailchimp has been installed since early 2020.

One strain of thought is that it might be caused with a high load of records from the mailchimp_sync_ecommerce table. It has about 400k records of which about 55k still have a mailchimp_sent = 0.

My questions:

1. Could you indicate what the cron mentioned above + the database table have for a purpose?

2. Is it 'normal' that there are 55k of records that have mailchimp_sent = 0?

3. Might mailchimp be causing this high load due to iterating over these unsend records? I have some issue in finding this in the cron Ecommerce.php code.

4. What is mailchimp actually changing that puts the indexer to work?

5. Also we were wondering what the impact might of clearing all the mailchimp tables both technically and business-wise. Sort of like a reset of the full mailchimp module (except for maybe the mailchimp_stores table ofcourse)

Thanks in advance!

[jdereus87]

Some thoughts into this from Mailchimp would be welcome