SELECT 
  COUNT(id) 
FROM 
  cscart_product_variation_disabled_variants 
WHERE 
  group_id = 1132 
  AND variant_id = '3980'

Query time 0.00089

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.57"
    },
    "table": {
      "table_name": "cscart_product_variation_disabled_variants",
      "access_type": "ALL",
      "rows_examined_per_scan": 218,
      "rows_produced_per_join": 2,
      "filtered": "1.00",
      "cost_info": {
        "read_cost": "22.35",
        "eval_cost": "0.22",
        "prefix_cost": "22.57",
        "data_read_per_join": "1K"
      },
      "used_columns": [
        "id",
        "group_id",
        "variant_id"
      ],
      "attached_condition": "((`cscartdb`.`cscart_product_variation_disabled_variants`.`group_id` = 1132) and (`cscartdb`.`cscart_product_variation_disabled_variants`.`variant_id` = '3980'))"
    }
  }
}