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 (
    70722, 70721, 70720, 70719, 70718, 70723, 
    70800, 79640, 79641, 79647, 79650, 
    79651, 80876, 80878, 80879, 80880, 
    80881, 80877, 84125, 84128, 84130, 
    84129, 84126, 84127, 84291, 84766, 
    84292, 84293, 84401, 84402, 84403, 
    84404, 86606, 86607, 86608
  )

Query time 0.00304

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": 35,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70722,70721,70720,70719,70718,70723,70800,79640,79641,79647,79650,79651,80876,80878,80879,80880,80881,80877,84125,84128,84130,84129,84126,84127,84291,84766,84292,84293,84401,84402,84403,84404,86606,86607,86608)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}