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 (
    9556, 9359, 9557, 9517, 6360, 9574, 1600, 
    9520, 1596, 9575, 9515, 1914, 9480, 
    9583, 1595, 9584, 9573, 9324, 9522, 
    1783, 9527, 2077, 9503, 6869, 9748, 
    9749, 9588, 1558, 9791, 3037, 3442, 
    1682, 9868, 9869, 9397, 1560, 9523, 
    9692, 9895, 1707, 9896, 9897, 9694, 
    9872, 9486, 9356, 1889, 9361, 9971, 
    1674, 9972, 9595, 9341, 1754, 9346, 
    9802, 9627, 9444
  )

Query time 0.00123

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "60.91"
    },
    "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": 58,
          "rows_produced_per_join": 58,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`pfv`.`variant_id` in (9556,9359,9557,9517,6360,9574,1600,9520,1596,9575,9515,1914,9480,9583,1595,9584,9573,9324,9522,1783,9527,2077,9503,6869,9748,9749,9588,1558,9791,3037,3442,1682,9868,9869,9397,1560,9523,9692,9895,1707,9896,9897,9694,9872,9486,9356,1889,9361,9971,1674,9972,9595,9341,1754,9346,9802,9627,9444))",
          "cost_info": {
            "read_cost": "34.81",
            "eval_cost": "5.80",
            "prefix_cost": "40.61",
            "data_read_per_join": "66K"
          },
          "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": 58,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "14.50",
            "eval_cost": "5.80",
            "prefix_cost": "60.91",
            "data_read_per_join": "175K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}