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 (
    1674, 9521, 2077, 9517, 1560, 1596, 1600, 
    9520, 9619, 9359, 9575, 9746, 9522, 
    9486, 9524, 6360, 9523, 9797, 9871, 
    9872, 3037, 1783, 9692, 3442, 9588, 
    1558, 9607, 9966, 9967, 9895, 9325, 
    9627, 9970, 9329, 9516, 9596, 9408, 
    9324, 9487, 1889, 10060, 9529, 9870, 
    6869, 10066, 9426
  )

Query time 0.00143

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "48.31"
    },
    "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": 46,
          "rows_produced_per_join": 46,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`pfv`.`variant_id` in (1674,9521,2077,9517,1560,1596,1600,9520,9619,9359,9575,9746,9522,9486,9524,6360,9523,9797,9871,9872,3037,1783,9692,3442,9588,1558,9607,9966,9967,9895,9325,9627,9970,9329,9516,9596,9408,9324,9487,1889,10060,9529,9870,6869,10066,9426))",
          "cost_info": {
            "read_cost": "27.61",
            "eval_cost": "4.60",
            "prefix_cost": "32.21",
            "data_read_per_join": "52K"
          },
          "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": 46,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "11.50",
            "eval_cost": "4.60",
            "prefix_cost": "48.31",
            "data_read_per_join": "139K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}