Understanding mega users in Fullstory

What are mega users? How are they created?

When the same user ID (uid) is set for more than one individual with the Identify Users API, Fullstory will coalesce these individuals and their sessions into the same user—this can be helpful when you have a single individual who uses your site or app on different devices and browsers. In cases where there are a large number of different individuals who have the same uid set, it can lead to the creation of what we call a mega user.

Mega users occur when an exceptionally high number of sessions are linked to a single uid. This can sometimes be attributed to our Identify Users API being set up or used incorrectly, or the usage of automated testing or bots.

Note: We officially released V2 of our Identify Users Browser API (e.g. setIdentity) on November 1st, 2023. If you're still using V1 of our Browser API (e.g. FS.identify), please refer to our V1 API documentation found here

If you were using Fullstory prior to August 3rd, 2023 and aren't sure which version of our Browser API is compatible with the data capture snippet deployed on your website, please refer to these instructions to confirm. 

Mega users are flagged in Fullstory when these specific thresholds are met:

  • Surpassing 250 unique cookies associated with a single uid in a day
  • Exceeding a consistent limit of 45 unique cookies for one uid

Once the count of coalesced individuals (cookies) for a single user reaches one of the above thresholds, the user is flagged as a mega user. When this happens, we will stop coalescing new sessions associated with the mega user uid into a single user card. Instead, you'll see each subsequent session splits into separate user cards, despite having the same uid.

Here is what this could look like when searching by the uid of a mega user:

megausers.png

 

The rationale behind splitting mega user cards

Our approach to ultimately splitting user cards stems from the fact that Fullstory uses shards for data segmentation. Using shards helps our search infrastructure process the data we store more efficiently and effectively. In the case of mega users, the sheer volume of sessions attributed to one user results in a single shard becoming overwhelmingly large, hindering efficient query processing. Moreover, an excessively amplified shard poses a challenge to data retrieval speed and may impact not only the concerned account, but it can also affect the performance of other Fullstory accounts with user data on the same shard. In your Fullstory account, this might manifest as sluggish or failed session loading experiences.

It's important to note that mega users from one customer account can impact the overall Fullstory experience in other customers’ accounts by overloading the search infrastructure and data storage shared across the platform. Recognizing the wider implications, it becomes vital to identify and manage mega user occurrences as quickly as possible. If a mega user arises, mitigating it often requires a collaborative effort between Fullstory and its customers.

What causes mega users?

There are a handful of common scenarios that can lead to the creation of mega users:

  • Improper implementation or usage of FS.identify (v1) or setIdentity (v2) is often a root cause.
  • Automated testing or bots may inadvertently trigger mega users.
  • Credential-sharing where an excessive number of individuals utilize the same login credentials.

 

How can we resolve mega users?

Addressing mega users first involves stopping their creation, and then permanently deleting existing mega users, including all of their related sessions. Taking these steps as quickly as possible helps us avoid performance degradation in the account in question, as well as possible impacts across other customers' accounts.

If mega users are detected in your account, they require immediate attention in the following ways:

  • Implementation of FS.identify (v1) or setIdentity (v2) will need to be updated to set only unique uid's for all users, and/or removing any Identify User API calls that set the same fixed uid for more than one individual user, or for anonymous users
  • Once your implementation of the Identify User API has been updated, we will need to process a permanent deletion on our end of all mega users, including all of their sessions

 If you detect mega users in your account, please reach out to our Support team here.

 


Was this article helpful?

Got Questions?

Get in touch with a Fullstory rep, ask the community or check out our developer documentation.