Scalable Web Messaging Inbox Design

I need a messaging-app style inbox that runs smoothly on the Web today and can grow without headaches tomorrow. At its core the inbox must show clear unread-message counters and provide fast, reliable search across conversations; message archiving is not in scope for this phase.

Beyond the user-facing features, I care about an architecture that can handle sudden traffic spikes, lets me shard or add queues easily, and keeps response times low as the user base grows. An API-first approach is preferred so mobile clients (iOS/Android) can be added later without re-engineering the server.

Deliverables
• High-level technical design (data model, service boundaries, scaling strategy)
• Wireframes or UI mock-ups illustrating unread counters and search workflow
• Recommended tech stack with reasoning (e.g., DB choice, indexing/search engine, caching layer)
• Implementation roadmap with milestones and clear acceptance criteria for each stage

Current web stack : Laravel + Vue
Theme : tailadmin.com