SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a720a1927536051a411e5a1527bb59597bed8a4830cea200fdc259e4b112558' 
  AND token = 'mfspO4cwYzrqXUuw8aAcB+QtYTU4TqosXFCS+Brai4k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}