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 (
    1748, 1660, 1705, 2122, 1973, 1989, 2325, 
    1975, 1659, 2348, 2345, 2347, 2007, 
    1706, 1941, 1712, 2341, 2343, 1942, 
    1983, 2344, 1899, 1998, 2336, 1902, 
    1992, 2342, 1937, 1972, 1980, 2334, 
    1974, 1994, 1926, 1904, 1945, 1787, 
    1789, 1995, 1900, 1988, 1742, 1905, 
    1946
  )

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "46.21"
    },
    "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": 44,
          "rows_produced_per_join": 44,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (1748,1660,1705,2122,1973,1989,2325,1975,1659,2348,2345,2347,2007,1706,1941,1712,2341,2343,1942,1983,2344,1899,1998,2336,1902,1992,2342,1937,1972,1980,2334,1974,1994,1926,1904,1945,1787,1789,1995,1900,1988,1742,1905,1946))",
          "cost_info": {
            "read_cost": "26.41",
            "eval_cost": "4.40",
            "prefix_cost": "30.81",
            "data_read_per_join": "50K"
          },
          "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": 44,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "11.00",
            "eval_cost": "4.40",
            "prefix_cost": "46.21",
            "data_read_per_join": "137K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}