Adafruit 24LC32 I2C EEPROM Breakout - 32Kbit / 4 KB - Stemma QT

If you want to store calibration values, MAC addresses, non-secure access tokens, or other unique identifiers, EEPROM storage is a great option. EEPROM is long lasting, and doesn't need to be written in pages - a single byte can be written at once (unlike with flash memory!) EEPROM storage persists even when the power goes out, and can be over-written literally one million times.