SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50885f2f4563e314394b2512cebb3b2756cc4d21a8a455d8ebd762374fea578c' 
  AND token = 'bSZIbwUtOVLIWDBedYo9qCEkILOqg2CHtYhxrdNVXYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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