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 (
    70578, 70577, 70579, 70584, 70583, 70645, 
    70644, 70643, 70642, 70641, 70659, 
    70658, 70657, 70656, 70655, 70680, 
    70679, 70678, 70677, 70676, 72397, 
    72398, 73131, 73130, 73129, 73132, 
    73136, 73135, 73134, 73133, 73137, 
    73183, 73182, 73181, 73180, 73184, 
    73205, 73204, 73206, 81493, 81494, 
    82402, 82406, 82405, 82404, 82403, 
    84766, 84292, 84293
  )

Query time 0.00897

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": 49,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70578,70577,70579,70584,70583,70645,70644,70643,70642,70641,70659,70658,70657,70656,70655,70680,70679,70678,70677,70676,72397,72398,73131,73130,73129,73132,73136,73135,73134,73133,73137,73183,73182,73181,73180,73184,73205,73204,73206,81493,81494,82402,82406,82405,82404,82403,84766,84292,84293)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}