Common Product Requirements

# Product Requirements Specification: App Performance

**Proposed file:** `docs/prd/prd-app-performance.md`  
**Feature status:** Draft — pending Discovery decisions  
**Linked BRD objective:** TBD  
**Product owner:** TBD  
**Engineering owner:** TBD  
**QA/release owner:** TBD  

## Discovery assumptions

- **What outcome:** Improve perceived and measured responsiveness so users complete key tasks with fewer delays and abandons.
- **Which channels:** Assume web and mobile. Confirm: a) Web only, b) Mobile only, c) Both.
- Primary persona: active authenticated customers. Confirm persona/JTBD.
- Baseline metrics, supported devices, geographic regions, offline requirements, and rollout constraints are TBD.

## Success metrics

Measure against the current production baseline:

- p75 cold app startup: ≤ 2 seconds.
- p75 navigation to an interactive screen: ≤ 1 second.
- p75 API response time for critical reads: ≤ 500 ms.
- p95 API response time for critical reads: ≤ 1,000 ms.
- Core Web Vitals, where applicable: LCP ≤ 2.5 seconds and INP ≤ 200 ms at p75.
- Reduce performance-related session abandonment by ≥ 15%.
- No increase in crash rate, error rate, or support contacts.

## Scope

### In scope

- Startup and initial rendering.
- Navigation and critical user journeys.
- Critical API requests and payload sizes.
- Loading, empty, and error states.
- Performance analytics, dashboards, guardrails, and rollout monitoring.

### Out of scope

- New product capabilities.
- Visual redesign unrelated to responsiveness.
- Replacing the database or hosting platform without evidence from profiling.
- Offline-first support unless selected during Discovery.

## Requirements

| ID | Requirement | Owner | Status | Priority | Verification lane | BRD objective |
|---|---|---|---|---|---|---|
| REQ-001 | The app shall identify and optimize the top three slowest critical journeys using representative production telemetry. | Engineering | Proposed | P0 | Performance test | TBD |
| REQ-002 | The app shall display an interactive initial experience within the target startup and navigation budgets for supported platforms and devices. | Engineering | Proposed | P0 | E2E and field telemetry | TBD |
| REQ-003 | Critical API calls shall meet the response-time budgets and shall avoid unnecessary duplicate requests. | Engineering | Proposed | P0 | API/load test | TBD |
| REQ-004 | Critical screens shall provide intentional loading, zero-state, timeout, and error experiences without blocking unrelated navigation. | Product + Engineering | Proposed | P1 | Manual QA and E2E | TBD |
| REQ-005 | The product shall capture performance metrics segmented by platform, app version, device class, geography, and network type where available. | Product Analytics | Proposed | P0 | Analytics validation | TBD |
| REQ-006 | Release readiness shall include performance regression checks against the approved baseline. | QA/Release | Proposed | P0 | CI/release verification | TBD |
| REQ-007 | Performance improvements shall preserve existing authorization, privacy, data integrity, and API compatibility requirements. | Engineering + Security | Proposed | P0 | Security and regression test | TBD |

## Acceptance criteria

### AC-001 — Baseline and prioritization

- **Given** production telemetry is available  
  **When** the performance assessment is completed  
  **Then** the team documents the baseline, top three slow journeys, affected platforms, and measurable target for each.

### AC-002 — Startup

- **Given** a supported device and representative network  
  **When** a user cold-starts the app  
  **Then** the first usable experience is available at or below the agreed p75 startup target.

### AC-003 — Navigation

- **Given** a user selects a critical destination  
  **When** navigation begins  
  **Then** the destination becomes interactive within the agreed p75 navigation target, or a clear progress state is shown.

### AC-004 — API performance

- **Given** a critical API request  
  **When** it is made under representative load  
  **Then** p75 and p95 latency meet the approved budgets, and the request is not duplicated without a documented reason.

### AC-005 — Loading and error states

- **Given** a critical screen is loading, empty, timed out, or receives an error  
  **When** the corresponding state occurs  
  **Then** the user sees an understandable state with an available recovery action where appropriate.

### AC-006 — Analytics

- **Given** a supported production session  
  **When** startup, navigation, API, or error events occur  
  **Then** the required events include app version, platform, device class, network type where available, duration, and success/failure outcome without collecting sensitive payload data.

### AC-007 — Regression protection

- **Given** a candidate release  
  **When** performance verification runs  
  **Then** no critical journey regresses beyond the agreed tolerance, assumed to be 10%, without Product and Engineering approval.

### AC-008 — Security and compatibility

- **Given** performance optimizations such as caching, prefetching, batching, or payload changes  
  **When** they are enabled  
  **Then** authorization boundaries, freshness rules, privacy controls, and existing API consumers remain correct.

## Analytics and operations

Recommended events:

- `app_start_completed`
- `screen_interactive`
- `navigation_completed`
- `api_request_completed`
- `performance_error`
- `performance_budget_exceeded`

Guardrails:

- Crash-free sessions.
- API error rate.
- Authentication failure rate.
- Data freshness and cache invalidation failures.
- Performance by release cohort.

Provide a dashboard and alert thresholds before rollout. Support documentation must explain known slow paths and recovery steps.

## Rollout

1. Establish baseline and instrumentation.
2. Validate improvements in development and staging.
3. Release to an internal cohort.
4. Expand to 5%, 25%, and 100% of eligible traffic.
5. Pause or roll back if guardrails regress or performance targets are missed.
6. Review results after seven days at full rollout.

## Risks and dependencies

- Results may vary by device, geography, and network quality.
- Caching or prefetching may increase data staleness or usage costs.
- Payload reduction may affect older clients.
- Instrumentation must avoid sensitive data.
- Database schema or API changes are TBD and require technical review if profiling identifies them as necessary.
- Offline mode is TBD; default assumption is graceful online failure handling, not offline-first behavior.

## RACI

- **Product:** Accountable for the What outcome, scope, targets, and rollout decision.
- **Engineering:** Responsible for profiling, implementation, API behavior, and technical evidence.
- **QA/release:** Responsible for acceptance testing, regression verification, and release sign-off.
- **Security/privacy:** Consulted on caching, telemetry, authorization, and data handling.
- **Support/Operations:** Consulted on dashboards, alerts, and customer communication.

## Decisions needed

1. Which channels: web, mobile, or both?
2. Which persona and critical journeys are highest priority?
3. What is the linked BRD objective and current baseline?
4. Is offline mode required?
5. Are API, database, or hosting changes permitted?

## Readiness and next workflow

The feature is not ready for engineering handoff until every slice has a `REQ-*`, `AC-*`, owner, status, priority, and verification lane, with baseline evidence and named validation owners.

Next workflow: `implementation-readiness`. After approval, determine whether `design-solution` is required for API, database, caching, or architecture changes.