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 (
    1137, 1134, 1138, 1136, 1146, 1148, 1147, 
    1145, 1173, 1174, 1153, 1156, 1266, 
    1269, 1268, 1267, 1264, 1265, 1255, 
    1253, 1259, 1256, 4698, 4697, 4696, 
    4695, 4694, 4693, 4692, 4707, 4706, 
    4705, 4704, 4703, 4702, 4701, 4700, 
    4699, 4710, 4709, 4708, 4711, 4712, 
    5884, 5867, 5868, 5885, 5886, 5887, 
    5888, 5889, 5985, 5986, 5987, 5988, 
    5989, 5990
  )

Query time 0.00133

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "59.86"
    },
    "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": 57,
          "rows_produced_per_join": 57,
          "filtered": "100.00",
          "index_condition": "(`cscartdb`.`pfv`.`variant_id` in (1137,1134,1138,1136,1146,1148,1147,1145,1173,1174,1153,1156,1266,1269,1268,1267,1264,1265,1255,1253,1259,1256,4698,4697,4696,4695,4694,4693,4692,4707,4706,4705,4704,4703,4702,4701,4700,4699,4710,4709,4708,4711,4712,5884,5867,5868,5885,5886,5887,5888,5889,5985,5986,5987,5988,5989,5990))",
          "cost_info": {
            "read_cost": "34.21",
            "eval_cost": "5.70",
            "prefix_cost": "39.91",
            "data_read_per_join": "65K"
          },
          "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": [
            "cscartdb.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 57,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "14.25",
            "eval_cost": "5.70",
            "prefix_cost": "59.86",
            "data_read_per_join": "172K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}