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 (
    68434, 68435, 68433, 70491, 70492, 71092, 
    71091, 71090, 71089, 71088, 71087, 
    71086, 71093, 71100, 71099, 71098, 
    71097, 71096, 71095, 71094, 71101, 
    73485, 73484, 75180, 75181, 75649, 
    75650, 75651, 76046, 76709, 76708, 
    76707, 76710, 77488, 77489, 77490, 
    79145, 79149, 79146, 79147, 79148, 
    79358, 79359, 79433, 79432, 84147, 
    84148, 84149
  )

Query time 0.01463

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": 48,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68434,68435,68433,70491,70492,71092,71091,71090,71089,71088,71087,71086,71093,71100,71099,71098,71097,71096,71095,71094,71101,73485,73484,75180,75181,75649,75650,75651,76046,76709,76708,76707,76710,77488,77489,77490,79145,79149,79146,79147,79148,79358,79359,79433,79432,84147,84148,84149)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}