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 (
    68495, 68905, 68906, 72403, 72404, 73587, 
    73586, 74561, 74562, 74560, 78640, 
    78639, 79424, 79423, 81440, 81445, 
    81446, 81447, 81441, 81442, 81443, 
    81444, 82029, 82030, 82031, 84066, 
    84065, 84069, 84068, 84067, 84630, 
    84629, 84628, 84627, 84626, 84625, 
    84624, 84623, 84633, 84632, 84631, 
    84622, 86290, 86291
  )

Query time 0.01036

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": 44,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68495,68905,68906,72403,72404,73587,73586,74561,74562,74560,78640,78639,79424,79423,81440,81445,81446,81447,81441,81442,81443,81444,82029,82030,82031,84066,84065,84069,84068,84067,84630,84629,84628,84627,84626,84625,84624,84623,84633,84632,84631,84622,86290,86291)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}