What would you do if, all of a sudden, our web traffic dropped by 100%?

Venmo is a payment application that allows me to create and share payment links, make purchases, transfer money to my bank account and to connect with people in the space. 

• 100% is a very significant drop, and it's alarming since it is a sudden drop

• However, it affected only the web traffic

• More clarifying questions I would ask the interviewer are:

  • What is the split between mobile & web traffic? Is there any change caused to the mobile traffic?

  • Are direct web traffic metrics like website visitors, logins etc impacted or indirect metrics like number of payments made, payment links shared, purchases made etc are impacted

  • All or specific OS, all or specific browsers 

Once I have a narrowed down the problem space, I would now like to list the possible root causes.

• Tech 
  • Does the URL work? Hosting issues, domain license issues, partner license issues 
  • Did a service or API powering the web app go down? 
  • Did we do a latest deployment that caused this? 
  • Did we release any new features that might have caused this? 
  • Did a partner payment system such as Bank or PG go down that affected us? 
• Data 
  • Did we make any recent changes to how we store or report the data from the website?
  • Is the data reporting tool working fine? 
• Marketing 
  • Did we run a new campaign that has not been implemented properly, like deep-linked or attributed incorrectly 

• A bureaucratic change happened in the country like demonatization 
• Regulations have changed on how money can be moved between Venmo and other payment partners in the ecosystem

• I would mail my entire team and cross-functional teams that the metric has gone down and we are working on identifying the root cause 
• Call in a meeting with the engg who are service owners of the APIs and debug the root cause 
• Message the devops teams, analytics teams and marketing teams to check for releases, deployments, marketing campaigns etc to identify the root cause 
• Once the root cause has been identified then circle back to all stakeholders, cross-functional teams who get impacted by this metric the entire report on the drop in metric, root cause and resolution taken and a turn around time before this metric will be healthy again.