SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b90301cb401408f6470ae093eef60ba672dbdb722e400aa786835503ef082da' 
  AND token = '5jPfL26D/tlKkytxVFws/DJWGq8L1/K0gnrgCaXjrBM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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