SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9f63899decdcffc3bc298560ac7f0621b9805ecc8e32e30247722df339d81345' 
  AND token = 'tnUP/XNTsd4ZRz5maMPQbQYipiA8Idye+sEXbCvwklM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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