SELECT 
  c.category_id as 'id', 
  n.name as 'name', 
  n.path as 'path', 
  c.link_type as 'type' 
FROM 
  cscart_products_categories as c 
  LEFT JOIN cscart_seo_names as n ON n.object_id = c.category_id 
WHERE 
  c.product_id = 64682 
  AND c.link_type = 'M'

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "c",
      "access_type": "ref",
      "possible_keys": ["link_type", "pt"],
      "key": "pt",
      "key_length": "6",
      "used_key_parts": ["product_id", "link_type"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "c.link_type = 'M'",
      "using_index": true
    },
    "table": {
      "table_name": "n",
      "access_type": "ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["object_id"],
      "ref": ["cscart_migrate.c.category_id"],
      "rows": 1,
      "filtered": 100
    }
  }
}

Result