SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f21e0787103f60a148d59f928a658274183c3a1444b5e4a9d8d43c79d655756' 
  AND token = 'BJb0X7zCYHGINE29+u43ExNI9tnXt7u3UYo5m4uXrKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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