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 (
    69876, 69875, 69874, 69873, 69872, 69877, 
    70745, 70746, 73475, 73474, 74213, 
    74212, 74214, 74841, 74840, 74838, 
    74837, 78608, 78609, 86290, 86291, 
    86311, 86310, 86309
  )

Query time 0.00427

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": 24,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (69876,69875,69874,69873,69872,69877,70745,70746,73475,73474,74213,74212,74214,74841,74840,74838,74837,78608,78609,86290,86291,86311,86310,86309)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}