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 = 'en' 
WHERE 
  pfv.variant_id IN (
    68399, 68398, 68400, 68827, 68826, 68828, 
    69749, 69748, 69750, 70722, 70721, 
    70720, 70719, 70718, 70723, 71204, 
    71205, 74204, 74203, 78274, 78273, 
    78272, 78271, 78270, 78275, 78476, 
    78472, 78473, 78474, 78475, 79220, 
    79222, 79221, 84766, 84292, 84293, 
    84291, 85226
  )

Query time 0.01720

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": 38,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68399,68398,68400,68827,68826,68828,69749,69748,69750,70722,70721,70720,70719,70718,70723,71204,71205,74204,74203,78274,78273,78272,78271,78270,78275,78476,78472,78473,78474,78475,79220,79222,79221,84766,84292,84293,84291,85226)"
        }
      },
      {
        "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 = 'en'"
        }
      }
    ]
  }
}