SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8a04598c10f62b60fc37b7219398dcdb4ae4b5fb89c84d90b8b8c8f77741339' 
  AND token = 'kJLzwU0HzrI8KYiQUBg+Gmep+Qu8HAjiZ1qixMVqUZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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