Custom extranet for legal cases processing

How to balance performances and usability while preserving dataset and workflows complexity?
Technologies: 
Symfony / SolR / Tika / LDAP / LemonLDAP
Context: 
Heavy resources load with always at least 1000 unique visitors on portal.
Back-end users struggled during case input with more than 200 different fields.
Current research capabilities deemed insufficient to find information.
Any adaptation of the extranet was a challenge.
Objectives: 
Improve research efficienty through faceted (multi-criterias) requests.
Render workflows and field complexity as transparent as possible for legal counsellors.
Ease user experience through simplified submission forms
Make the extranet maintenable and adaptable by internal team.
Missions: 
Redefine data models, displays and workflow in YAML files.
Deploy and configure advanced search engine SolR and metadata extractor TIKA.
Integrate LemondLDAP to provide Single Sign-On to everyone.
Design custom user interfaces for back-end and front-end.
Benefits: 
Administration gains autonomy in extranet lifecyle.
Data complexity is now tempered by flexible search system.
LemonLDAP integration facilitates user management between several applications.
Workflows are configured into the extranet to ease advancement monitoring.