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 (
    70249, 70248, 70247, 70246, 70245, 70244, 
    70243, 70242, 70241, 71589, 71588, 
    71587, 71586, 71585, 71590, 71601, 
    71600, 71599, 71598, 71602, 71610, 
    71609, 71608, 71607, 71606, 71605, 
    71604, 71603, 71611, 71616, 71614, 
    71613, 71612, 71615, 72337, 72336, 
    72338, 75462, 75461, 79032, 79033, 
    80579, 80578, 81269, 81270, 81643, 
    81644, 86606, 86607, 86608
  )

Query time 0.00362

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": 50,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70249,70248,70247,70246,70245,70244,70243,70242,70241,71589,71588,71587,71586,71585,71590,71601,71600,71599,71598,71602,71610,71609,71608,71607,71606,71605,71604,71603,71611,71616,71614,71613,71612,71615,72337,72336,72338,75462,75461,79032,79033,80579,80578,81269,81270,81643,81644,86606,86607,86608)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}