Many information systems are used in a problem solving context. Examples are travel planning systems, catalogs in electronic commerce, or agenda planning systems. They can be made more useful by integrating problem-solving capabilities into the information systems. This poses the challenge of scaleability: when hundreds of users access a server at the same time, it is important to avoid excessive computational load. We present the concept of SmartClients: lightweight problem-solving agents based on constraint satisfaction which can carry out the computation- and communication-intensive tasks on the user's computer. We present an example of an air travel planning system based on this technology.