SELECT 
  COUNT(id) 
FROM 
  cscart_product_variation_disabled_variants 
WHERE 
  group_id = 3065 
  AND variant_id = '6024'

Query time 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "41.93"
    },
    "table": {
      "table_name": "cscart_product_variation_disabled_variants",
      "access_type": "ALL",
      "rows_examined_per_scan": 409,
      "rows_produced_per_join": 4,
      "filtered": "1.00",
      "cost_info": {
        "read_cost": "41.52",
        "eval_cost": "0.41",
        "prefix_cost": "41.93",
        "data_read_per_join": "3K"
      },
      "used_columns": [
        "id",
        "group_id",
        "variant_id"
      ],
      "attached_condition": "((`chocoramo`.`cscart_product_variation_disabled_variants`.`group_id` = 3065) and (`chocoramo`.`cscart_product_variation_disabled_variants`.`variant_id` = '6024'))"
    }
  }
}