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 (
    3037, 9517, 1596, 1674, 9590, 1600, 9523, 
    9524, 9751, 9522, 9753, 9588, 9045, 
    9866, 9796, 9503, 9408, 6360, 9870, 
    9692, 9516, 1914, 1783, 9321, 1682, 
    9426, 9556, 6869, 9398, 8285, 9349, 
    9637, 9557, 1558
  )

Query time 0.00108

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "35.71"
    },
    "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": 34,
          "rows_produced_per_join": 34,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`pfv`.`variant_id` in (3037,9517,1596,1674,9590,1600,9523,9524,9751,9522,9753,9588,9045,9866,9796,9503,9408,6360,9870,9692,9516,1914,1783,9321,1682,9426,9556,6869,9398,8285,9349,9637,9557,1558))",
          "cost_info": {
            "read_cost": "20.41",
            "eval_cost": "3.40",
            "prefix_cost": "23.81",
            "data_read_per_join": "38K"
          },
          "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": [
            "softwarepirmam_hewadelivard_cscart_4.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 34,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "8.50",
            "eval_cost": "3.40",
            "prefix_cost": "35.71",
            "data_read_per_join": "102K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}