We've used the following technologies to build our application:

• NextJS for front-end with TailwindCSS for styling
• Python + Flask for back-end API and cron job
• MongoDB for database Courier for sending notifications

The user first gets to the homepage, where he has to select his origin, destination and date of travel. Once they click on the "Search Cheapest Flight" button, they'll be redirected to flight details page. Here once the page is loaded, the GET /flight-price API is called. This API requires the origin and destination's IATA code (International Air Transport Association), and the travel date. The IATA code of all active US airports are stored in a JSON file in the front end, including other airport details such as ICAO code, name, city, etc. These details are then sent to Skyscanner API, which returns all the bookings available on that particular day from different airline and travel agency websites. The data sent by skyscanner contains various fields like airport details, price, itinerary legs, carrier details, etc. In the backend, we sort the list by price, and extract several details like number of stops, arrival time, departure time, flight time, airline details, etc. Then the cheapest flight's data along with the other extracted data is saved into a database, and also sent back to the front-end where it is displayed to the user. Now the user can see the flight details, and also gets an option to subscribe to notifications. When user enters their details (email and mobile number) and clicks on "Subscribe", the POST /flight-price-subscribe API is called which stores the details in database relevant to their search query. In the background, a cron job is running which checks the price of tracked queries once in a while. This calls the check_flight_price() function which queries calls Skyscanner API and gets details of all the queries one by one. Then it checks for the price stored for that particular query in database. If the new price is lower, then the new details are extracted and replaces the previous details in database. It then checks for the subscribed users list in that query. By using Courier API, an email and SMS is sent to the user regarding price drop. The message contains the new price, old price, and even the link for booking the flight.