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 (
    1748, 1660, 1705, 2122, 1973, 1989, 2325, 
    1975, 1659, 2348, 2345, 2347, 2007, 
    1706, 1941, 1712, 2341, 2343, 1942, 
    1983, 2344, 1899, 1998, 2336, 1902, 
    1992, 2342, 1937, 1972, 1980, 2334, 
    1974, 1994, 1926, 1904, 1945, 1787, 
    1789, 1995, 1900, 1988, 1742, 1905, 
    1946, 2137, 2138, 2000, 2351, 2075, 
    1694, 2088, 2082, 2080, 2083, 2092, 
    2084, 2093, 2086, 2085, 2087, 2089, 
    1912, 2350, 2145, 2081, 2090, 2327, 
    1803, 2027, 2167, 2168, 2094, 2095, 
    2096, 2097, 2016, 2144, 2026, 2025, 
    2012, 2013, 2129, 2107, 2291, 2278, 
    2297, 2280, 2293, 2281, 2294, 2170, 
    2282, 2299, 2283, 2284, 2285, 2286, 
    2287, 2288, 1930, 1721, 2123, 1959, 
    1984, 2290, 1938, 2020, 2339, 2338, 
    2021, 2337, 1768, 1978, 2362, 1723, 
    1727, 2364, 2169, 2106, 2105, 2268
  )

Query time 0.00117

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "127.06"
    },
    "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": 121,
          "rows_produced_per_join": 121,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (1748,1660,1705,2122,1973,1989,2325,1975,1659,2348,2345,2347,2007,1706,1941,1712,2341,2343,1942,1983,2344,1899,1998,2336,1902,1992,2342,1937,1972,1980,2334,1974,1994,1926,1904,1945,1787,1789,1995,1900,1988,1742,1905,1946,2137,2138,2000,2351,2075,1694,2088,2082,2080,2083,2092,2084,2093,2086,2085,2087,2089,1912,2350,2145,2081,2090,2327,1803,2027,2167,2168,2094,2095,2096,2097,2016,2144,2026,2025,2012,2013,2129,2107,2291,2278,2297,2280,2293,2281,2294,2170,2282,2299,2283,2284,2285,2286,2287,2288,1930,1721,2123,1959,1984,2290,1938,2020,2339,2338,2021,2337,1768,1978,2362,1723,1727,2364,2169,2106,2105,2268))",
          "cost_info": {
            "read_cost": "72.61",
            "eval_cost": "12.10",
            "prefix_cost": "84.71",
            "data_read_per_join": "138K"
          },
          "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": 121,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "30.25",
            "eval_cost": "12.10",
            "prefix_cost": "127.06",
            "data_read_per_join": "377K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}