How would you go about launching a "video message" functionality in a communication app that gets used by over 100 million users?

Clarifying questions: 

Is this app in consumer space or corporate users? - Currently Consumer Space

Are we talking about 2 way video chat or recorded video messages - recorded video messages that users can send to each other.

What is the primary user segment for this app? -  age range of 18 to 35, who are tech-savvy and often use the app for social and casual communication

Any specific goal in mind when this feature was thought about? -  primary goal for introducing the "video message" functionality is to enhance user engagement and provide a more personal and interactive way for users to connect. 

Technical constraints for this feature, given that video messages are data heavy - ensuring a smooth user experience across various network conditions, including lower-bandwidth connections. There's also a concern about the storage and processing of large video files, both on the user's device and on our servers.

Does app has video chat functionality right now? - No

Here is my thought process. 

I am assuming that app is being used across many countries. I will be planning a phased launch. I will also not be expoloring corporate users for this discussion.

I will pick a country where network speed and mobile phone specifications are not a problem. We will divide our user cohorts on the bases of app usage. We will pick 2 cohorts: 

1 who use app on daily basis. Dau/mau ratio is close to 1. 

2nd Cohort - People who use it once in 2 days. 

Once we introduce the feature, following will be tracked. 

* Usage of feature(number of people using it, how many times they use it), 

* impact on text messages - Counter Metric

*  if overall engagement is going low or high. 

* Length of message. Overall, we ideally will have upper limit of X MB. 

* How people respond - Do they respond with Video chat or text chat. This will also help us understand the relative preference of users with different modes of communication

Among these cohorts, we will also set up an group discussion to get the feedback on feature launched.  

Next phase would be to launch in a country where we have nixed users in terms of devices or network speed. How this frature behaves when 1 person has good device and network while the recipient does not have great connectivity or device need to be tracked

Based on the user feedback and experience with low network capability markets, we can also explore following

When user is recording a video message, based on recipient’s network condition, we can give an option to record in lower resolution. We can also look at the maximum length of video message. There is one more aspect of to whom we should allow to send the video message. Recipient should have an option to accept from specific people or restrict specific people to reduce scope of unwanted messages. Once these problem are sorted and addressed, we can look for worldwide launch. Please note, in this phase, I have specifically avoided discussing video messages to group chats.