SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'vi' 
WHERE 
  pfv.variant_id IN (
    69833, 69832, 69848, 69847, 69849, 71077, 
    71078, 71082, 71081, 71083, 76836, 
    76835, 76837, 81150, 81151, 84666, 
    84665, 84664, 84663, 84696, 84697, 
    84698, 84699, 84700, 76880, 76881, 
    76885, 76884
  )

Query time 0.00335

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 28,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (69833,69832,69848,69847,69849,71077,71078,71082,71081,71083,76836,76835,76837,81150,81151,84666,84665,84664,84663,84696,84697,84698,84699,84700,76880,76881,76885,76884)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}