SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '397da92d774130533d151f7cd74001d45a1022e7729eda2a6681a52876a217df' 
  AND token = '5puJf/MtMqKu+cbKqqMsj8BuS5bHSgcm3X1e4iTrD+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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