SELECT 
  a.modifier, 
  a.modifier_type, 
  a.variant_id 
FROM 
  cscart_product_option_variants a 
WHERE 
  1 
  AND a.variant_id IN (
    7346, 7624, 2943, 2517, 2652, 2744, 3251, 
    3299
  )

Query time 0.00056

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.61"
    },
    "table": {
      "table_name": "a",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "variant_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 8,
      "rows_produced_per_join": 8,
      "filtered": "100.00",
      "index_condition": "(`cscartdb`.`a`.`variant_id` in (7346,7624,2943,2517,2652,2744,3251,3299))",
      "cost_info": {
        "read_cost": "4.81",
        "eval_cost": "0.80",
        "prefix_cost": "5.61",
        "data_read_per_join": "384"
      },
      "used_columns": [
        "variant_id",
        "modifier",
        "modifier_type"
      ]
    }
  }
}