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 (
    2334, 1705, 1660, 1789, 1659, 2098, 2325, 
    2043, 1912, 1803, 1748, 2327, 1973, 
    2083, 2092, 2101, 2085, 2100, 2088, 
    2087, 2099, 2000, 1937, 2016, 1995, 
    1902, 1900, 1904, 1945, 1787, 1905, 
    1946, 2075, 1899, 2292, 2293, 2294, 
    2285, 2312, 2286, 2311, 2026, 2310, 
    2284, 2002, 2029, 1721, 2337, 1998, 
    1876, 2025, 2001, 1680, 2341, 1679, 
    2368
  )

Query time 0.00196

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "58.81"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 56,
          "rows_produced_per_join": 56,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (2334,1705,1660,1789,1659,2098,2325,2043,1912,1803,1748,2327,1973,2083,2092,2101,2085,2100,2088,2087,2099,2000,1937,2016,1995,1902,1900,1904,1945,1787,1905,1946,2075,1899,2292,2293,2294,2285,2312,2286,2311,2026,2310,2284,2002,2029,1721,2337,1998,1876,2025,2001,1680,2341,1679,2368))",
          "cost_info": {
            "read_cost": "33.61",
            "eval_cost": "5.60",
            "prefix_cost": "39.21",
            "data_read_per_join": "63K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "gaseus.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 56,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "14.00",
            "eval_cost": "5.60",
            "prefix_cost": "58.81",
            "data_read_per_join": "174K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}