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 (
    2448, 2444, 2344, 2345, 2445, 1912, 2122, 
    1694, 2290, 1660, 2457, 2458, 2139, 
    1992, 1902, 2449, 2413, 2075, 2350, 
    2456, 2452, 2455, 2443, 1972, 1995, 
    2454, 2453, 1900, 1905, 1787, 2451, 
    2447, 2000, 1904, 2460, 1462, 2463, 
    1705, 2462, 2466, 2464, 2467, 2468, 
    2465, 2469, 2477, 2473, 1973, 1659, 
    2479, 2480, 2481, 2471, 1718, 2482, 
    1926, 2478, 2370, 2374, 1803, 2043, 
    2497, 2498, 2348, 2369, 2373, 1789, 
    2499, 1899, 2123, 1721, 2501, 2121, 
    1727, 2508, 1879, 2378, 2524, 1712, 
    1928
  )

Query time 0.00122

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "84.01"
    },
    "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": 80,
          "rows_produced_per_join": 80,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (2448,2444,2344,2345,2445,1912,2122,1694,2290,1660,2457,2458,2139,1992,1902,2449,2413,2075,2350,2456,2452,2455,2443,1972,1995,2454,2453,1900,1905,1787,2451,2447,2000,1904,2460,1462,2463,1705,2462,2466,2464,2467,2468,2465,2469,2477,2473,1973,1659,2479,2480,2481,2471,1718,2482,1926,2478,2370,2374,1803,2043,2497,2498,2348,2369,2373,1789,2499,1899,2123,1721,2501,2121,1727,2508,1879,2378,2524,1712,1928))",
          "cost_info": {
            "read_cost": "48.01",
            "eval_cost": "8.00",
            "prefix_cost": "56.01",
            "data_read_per_join": "91K"
          },
          "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": 80,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "20.00",
            "eval_cost": "8.00",
            "prefix_cost": "84.01",
            "data_read_per_join": "249K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}