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 (
    1659, 2100, 2016, 1721, 1973, 2337, 1803, 
    1660, 1900, 2085, 2101, 2098, 2327, 
    1748, 2083, 2092, 2099, 1912, 2087, 
    2088, 2325, 1705, 1789, 1998, 1899, 
    1876, 1945, 1904, 2025, 1905, 1787, 
    1946, 1937, 2002, 2001, 1680, 2341, 
    1679, 2000, 2026
  )

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "42.01"
    },
    "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": 40,
          "rows_produced_per_join": 40,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (1659,2100,2016,1721,1973,2337,1803,1660,1900,2085,2101,2098,2327,1748,2083,2092,2099,1912,2087,2088,2325,1705,1789,1998,1899,1876,1945,1904,2025,1905,1787,1946,1937,2002,2001,1680,2341,1679,2000,2026))",
          "cost_info": {
            "read_cost": "24.01",
            "eval_cost": "4.00",
            "prefix_cost": "28.01",
            "data_read_per_join": "45K"
          },
          "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": 40,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "10.00",
            "eval_cost": "4.00",
            "prefix_cost": "42.01",
            "data_read_per_join": "124K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}