The summary endpoint works by creating a page lead before running additional summary-specific transformations on it.
To reduce production load, we should use existing, cached page leads rather than creating them anew on each summary request.
- RESTBase does not expose tid as a path variable in the mobile-sections endpoints. If we move to using cached mobile-sections-lead responses from RESTBase we'll need to agree either on adding tid support in RESTBase for mobile-sections or updating the MCS summary endpoint not to use or advertise tid.
- T187098: Extra span at beginning of mobile-sections-lead (probably caused at least in some cases by our own lead paragraph shifting transform)