SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f796b557d2b77e71a4e9f6592fbdc32951edcb819f1317d565141f06294b9fdd' 
  AND token = 'IrUFjLCB8shQMZT1zXu1LbUFGfDalW3aTsYmBYguLKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}