SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4323797d75adf8a8a671909668ffaf83b49a58b866b59b2cd4c3f7b91ef2c78' 
  AND token = 'dhi8R6KCZDq4uyJ/7FuFK7OZ9IwWZ6xTyixLJnNSgJI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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