Design a cab-sharing service inside a chat application.

I'll first start with a few clarifying questions.

1. Can I pick any chat application or do you have any particular app in mind? You choose. I'll pick WhatsApp since it's widely used and has an active user base of around 2 billion.

2. I just want to bring both of us on the same page in terms of cab-sharing service. A cab-sharing service is one where users can come & book a cab at any time of the day or can pre-book cabs for a future time slot.

3. Are we considering just cabs or do we need to consider other modes of transportation as well like bikes, autos, rentals, etc? If I have to pick one, I'll start with just cabs & later expand to other modes after achieving product market fit.

4. Since we want to launch it inside Whatsapp itself, I am assuming it won't be a separate startup and we can leverage Whatsapp's existing features & draw synergies.

5. What is our goal in introducing cab sharing within WhatsApp? If I have to decide, I'll tie it back to the overall mission of WhatsApp which is to let people communicate freely. Given most of the conversations or plans are made with friends or family on calls or chats, introducing cab service provides vertical integration and allows the users to book cabs without leaving the platform and share live updates with the concerned people. Also, if we consider the drivers, most of them would already have Whatsapp installed on their mobile devices & won't need to install another app. They are also familiar with the interface & hence the learning curve of introducing a new cab service will be smaller. Our goal for launching cab-service would be to increase engagement on the platform & eventually revenue and not acquisition as we already have a huge user base. For starters, we'll keep engagement as the goal & later we will work on increasing revenue with this feature.

6. Are we going to follow a marketplace model or an inventory model? For most practical purposes it should be a marketplace model because WhatsApp has no other business in owning these cars.

7. Are we considering any particular geography in mind or should we cover it from a global angle? Since Whatsapp is a globally used app, all the features should be thought through from a global lens.

8. Are there any constraints we are working with in terms of money, time, or resources? No, you can assume there are no constraints.

9. Even though WhatsApp exists for both desktop & mobile devices, we'll launch cab sharing service on mobile only as the % of users using a desktop to book a cab is negligible.

10. My last point would be to think about the competitors & how WhatsApp can differentiate itself from them. Cab-service companies like Uber, Ola, Lyft, etc. are the direct competitors. WhatsApp can differentiate itself by being able to provide an ecosystem within the app where plans are being made and venue & timing are being decided. Users can accomplish more without switching apps.

Now thinking about the user segment:

1. Professional users: Users who use cabs to reach their offices almost on a daily basis.

2. Recreational users: Users who use cabs to meet with their friends, and family for a get-together. They can travel alone or pick up other people on the way.

3. Travellers: Users who are visiting another country or catching a flight.

I would pick recreational users as the target segment since that's where WhatsApp can add value. Professional users have a fixed destination where they have to travel every day & it is already being served well by the competitors. For travelers visiting another country, they will have to search for places to visit or have their friends recommend places that require a bigger circle whereas WhatsApp is a bit more personal.

Let us talk about the pain points of recreational users:

1. Users have to reach out to friends or family to make plans on call or create WhatsApp groups for the same. The place should be apt for the day, weather, purpose of visit, etc.

2. They mutually decide on a place based on & the time to meet and also if anyone will be accompanied by someone. Users normally want to know how much time each person will take to reach the place from their location and how far they have reached.

3. Users open another app like Uber or Ola to book a ride. They search for the place and book a cab by choosing a payment method (online/offline). Once the ride starts, they share the ride status with their friends or family to provide live tracking so that others are updated about your arrival time.

4. Users may need to share the ride status with their emergency contact to keep them updated if they are late or to the police if they don't feel safe.

Let us now talk about the solutions addressing these pain points and then we will prioritize.

I will prioritize solution 2 first since it solves a major use case for the users with low effort and will help differentiate WhatsApp from others.

The feature will be available as one of the options at the bottom of the chat window just like attachment, text box, etc. On clicking on the cab icon, the user gets taken to a separate page that has the map, search functionality, and payment options with one single option to book a cab. As soon as the 1st person in the group leaves their house, a map view appears which starts displaying the live location of the users. This process repeats when others leave & they get added to the same map.

Risks:

1. Since we are providing the live location of the user, we have to make sure that it doesn't get accessed by malicious or unintended users. This can be mitigated to some extent by disabling the map view once everyone reaches the location.

2. Since the feature will only be available on phones, we have to make sure that desktop chat history does not display live tracking since it could be accessed by anyone in the user's absence.

3. Security systems need to be encrypted to prevent breaches of user privacy.

Finally, I would like to touch upon the metrics to measure the success of the product. Since our overall goal, for now, is to increase engagement, we need to focus on those metrics.

1. North Star metric: DAU, MAU

2. Secondary metrics: Time spent on the app, No. of messages exchanged in 7D, 30D period, No. of reactions. The feature may cause a slight reduction in the messages exchanged as the follow-up messages get reduced but if the overall time spent on the app increases, we can consider that a success.

3. Feature-specific metrics: This includes funnel metrics. No. of users searching for a place, No. of users attempting to book a cab, No. of rides booked, and Impressions on the map view. 

I have covered the consumer experience side. Since it is going to be a marketplace, do you want me to cover the driver's side as well?

No, we can close here for now.