In Sandstorm, we are encoding powerbox queries in packed base64 strings which may be placed in URL query parameters or the like. The strings are provided in interfaces called browser-side. We anticipate that some developers will prefer to specify a hardcoded string rather than generate it on-the-fly, since Cap'n Proto is not well-supported in browsers today, and anyway the developer may have no other reason to have a Cap'n Proto dependency at all, and powerbox queries are often static.

In this context, speed is irrelevant, while having a compact encoding is desirable. It felt sad to me to leave in the segment table in this context, adding redundant bytes when we want a compact encoding.