For your needs, it is recommended to add another collection and use userId for association, although mongodb gives priority to inline processing. Since analyzing your activities is used to create a user activity timeline, it is basically something every user should have. In addition, according to your description, activities will put a lot of things. Although MongoDB currently expands the size of a single document to 16M, if the content is too large, it will still exceed its limit, and it will also have a certain impact on queries, etc. For this situation, mongodb will also recommend making redundant connections to simulate SQL connection queries.
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For your needs, it is recommended to add another collection and use userId for association, although mongodb gives priority to inline processing. Since analyzing your activities is used to create a user activity timeline, it is basically something every user should have. In addition, according to your description, activities will put a lot of things. Although MongoDB currently expands the size of a single document to 16M, if the content is too large, it will still exceed its limit, and it will also have a certain impact on queries, etc. For this situation, mongodb will also recommend making redundant connections to simulate SQL connection queries.