an ESP32 could be the heart of your system. it would offer a webserver (ESPAsyncWebServer) to interact with and would manager the sensors (RFID, distance sensor, ...) and actuators (gates...)
There is no real need for a formal database, just some canned structures in memory to represent all the parking spaces, the users etc.... if you need things to work post reboot, use the flash file system of the ESP32 and the Preferences library for example.