Additionally, the“architecture of assembly”and its extensive usage of third-party services might result in technical problems. APIs of a service can change and unlike traditional software there is no prior version to revert to. Additionally, rate limits can raise problems. Often, Web 2.0 services impose rate limits, e.g., by specifying a maximum number of request a client can send per hour. This can interfere with educational applications, for instance if interactions or content created by learners is to be downloaded for off-line analysis (see Section 3.1).