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SELECT 
  a.modifier, 
  a.modifier_type, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier, 
    a.modifier
  ) as modifier, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier_type, 
    a.modifier_type
  ) as modifier_type, 
  a.variant_id 
FROM 
  cscart_product_option_variants a 
  LEFT JOIN cscart_ult_product_option_variants shared_option_variants ON shared_option_variants.variant_id = a.variant_id 
  AND shared_option_variants.company_id = 1 
WHERE 
  1 
  AND a.variant_id IN (
    239949, 218476, 220232, 220264, 220240, 
    220241, 220271, 220303, 220307, 220309
  )

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "shared_option_variants",
      "access_type": "system",
      "possible_keys": ["PRIMARY", "company_id"],
      "rows": 0,
      "filtered": 0,
      "const_row_not_found": true
    },
    "table": {
      "table_name": "a",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["variant_id"],
      "rows": 10,
      "filtered": 100,
      "attached_condition": "a.variant_id in (239949,218476,220232,220264,220240,220241,220271,220303,220307,220309)"
    }
  }
}

Result

modifier	modifier_type	variant_id
0.000	A	218476
0.000	A	220232
0.000	A	220240
0.000	A	220241
0.000	A	220264
0.000	A	220271
0.000	A	220303
0.000	A	220307
0.000	A	220309
0.000	A	239949