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 (
    1787, 1660, 1705, 2334, 1912, 1706, 2325, 
    1938, 2290, 2344, 2345, 2347, 1748, 
    2122, 2348, 2349, 2145, 2027, 2350, 
    1989, 1712, 2021, 1803, 2129, 2007, 
    2327, 1975, 2144, 2000, 2016, 1900, 
    2075, 1899, 2025, 1905, 1937, 1988, 
    1946, 1789, 2338, 1904, 1945, 1941, 
    1942, 1998, 1972, 1974, 2341, 2020, 
    2023, 2018, 2017, 2339, 1995, 1742, 
    1694, 2013, 2012, 2342, 2022, 2026, 
    2019, 2024, 1659, 1973, 1983, 1926, 
    1902, 1935
  )

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "72.46"
    },
    "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": 69,
          "rows_produced_per_join": 69,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (1787,1660,1705,2334,1912,1706,2325,1938,2290,2344,2345,2347,1748,2122,2348,2349,2145,2027,2350,1989,1712,2021,1803,2129,2007,2327,1975,2144,2000,2016,1900,2075,1899,2025,1905,1937,1988,1946,1789,2338,1904,1945,1941,1942,1998,1972,1974,2341,2020,2023,2018,2017,2339,1995,1742,1694,2013,2012,2342,2022,2026,2019,2024,1659,1973,1983,1926,1902,1935))",
          "cost_info": {
            "read_cost": "41.41",
            "eval_cost": "6.90",
            "prefix_cost": "48.31",
            "data_read_per_join": "78K"
          },
          "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": 69,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "17.25",
            "eval_cost": "6.90",
            "prefix_cost": "72.46",
            "data_read_per_join": "215K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}