Detailed component design

redis as in memory cache
- keep tracking of expiration time. If expired, trigger a push notification to users.
message queues are used to decouple services
in API server, add locking mechanism to ensure that one spot can only be reserved by one customer.
1. Check Slot Availability in Database: When a booking request is received, the API server first checks the database to retrieve the slot information and determine if it is available.
2. Acquire Lock in Redis: Before proceeding with the booking, the server attempts to acquire a lock for the slot using Redis. This ensures that no other server can book the same slot simultaneously.
3. Check Redis for Booked Slots: Once the lock is acquired, the server checks Redis to see if the slot is already booked. If it's not booked, the server proceeds to book the slot.
  1. Book the Slot in Redis:If the slot is not already booked in Redis, the server marks the slot as booked by setting a key in Redis.
  2. Optionally, update the database to reflect the booking status for persistence.
4. Release Lock: After the booking is confirmed, the server releases the lock.
5. Handle Conflicts: If the slot is already booked in Redis or if the lock cannot be acquired, the server returns an appropriate response to the client, indicating that the slot is unavailable.

payment try queue and deadletter queue to handle failed payments and expired payments.