SELECT 
  CONCAT(u.firstname, ' ', u.lastname) as author, 
  b.page_id 
FROM 
  cscart_blog_authors as b 
  LEFT JOIN cscart_users as u ON b.user_id = u.user_id 
WHERE 
  b.page_id IN (
    444, 445, 441, 440, 439, 438, 443, 442, 
    437, 63, 64, 65, 62, 58, 59, 57, 41, 42, 
    43, 44
  )

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "b",
          "access_type": "index",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["page_id", "user_id"],
          "rows": 27,
          "filtered": 74.07407379,
          "attached_condition": "b.page_id in (444,445,441,440,439,438,443,442,437,63,64,65,62,58,59,57,41,42,43,44)",
          "using_index": true
        }
      },
      {
        "table": {
          "table_name": "u",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["user_id"],
          "ref": ["demov2026.b.user_id"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}