The backend solution for Namma Yatri auto booking without installing the app can be developed using the following technologies:

Using Twilio API, we can enable users to book an auto via SMS or WhatsApp. Customers can send a message with their pickup location and destination, and the backend can generate an automated response with driver availability and estimated fare.

A backend server needs to be set up to handle customer requests, store data, validate user input and process bookings. The server should also interact with the auto drivers' mobile phones in real-time to update them regarding new bookings.

The frontend solution for Namma Yatri auto booking without installing the app can be developed using the following technologies:

Developing a responsive website where users can book autos without the need for an app would cater to a vast majority of people who are comfortable accessing the internet. The website should have a simple and easy-to-use interface that allows customers to enter their pickup and drop-off locations, check availability and book a ride.

An SMS gateway can be set up to accept auto bookings via text messaging. Customers can send messages with their pickup location and destination to a designated Namma Yatri SMS number, and the backend can generate an automated response with driver availability and estimated fare.

In conclusion, using the above innovative tech solutions, customers can book an auto with Namma Yatri without having to install the app, which opens up more demand for the company.