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 = 'vi' 
WHERE 
  pfv.variant_id IN (
    68336, 68335, 68334, 68333, 68332, 68337, 
    71108, 71107, 71106, 71105, 71104, 
    71103, 71102, 71109, 71116, 71115, 
    71114, 71113, 71112, 71111, 71110, 
    71117, 71164, 71163, 71162, 71161, 
    71160, 71159, 71158, 71165, 71520, 
    71519, 71518, 71521, 71549, 71774, 
    71773, 72794, 72795, 73529, 73528, 
    74486, 74487, 74485, 76741, 76740, 
    76742, 77945, 77943, 77944, 78426, 
    78622, 78621, 79244, 79242, 79243, 
    81917, 81922, 81923, 81924, 81925, 
    81926, 81918, 81919, 81920, 81921, 
    86166, 86167, 86236, 86235, 86234, 
    86233, 86449, 86448, 86447, 86446, 
    86445, 86444, 86453, 86452, 86443, 
    86451, 86450
  )

Query time 0.00803

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 83,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68336,68335,68334,68333,68332,68337,71108,71107,71106,71105,71104,71103,71102,71109,71116,71115,71114,71113,71112,71111,71110,71117,71164,71163,71162,71161,71160,71159,71158,71165,71520,71519,71518,71521,71549,71774,71773,72794,72795,73529,73528,74486,74487,74485,76741,76740,76742,77945,77943,77944,78426,78622,78621,79244,79242,79243,81917,81922,81923,81924,81925,81926,81918,81919,81920,81921,86166,86167,86236,86235,86234,86233,86449,86448,86447,86446,86445,86444,86453,86452,86443,86451,86450)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}