Research: Evaluate Unleash as GrowthBook replacement

[wax911]

Investigation: Unleash vs GrowthBook Evaluation

Overview

Research findings on migrating from GrowthBook to Unleash as the feature flagging platform for on-the-edge and Local-Stack.

Current State

• SDK: @growthbook/growthbook@^1.2.2 (JSR, Deno-compatible)
• Integration: ExperimentService (src/experiment/) with per-request middleware
• Features: 9 boolean toggles + 2 value parameters (platform-source array, episode-align-title-sim numeric)
• Middleware: GrowthBookMiddleware initializes features per request

Key Findings

Unleash Architecture

• Open-source: Feature-complete, no payment-gated features
• Database: PostgreSQL-backed (required, no in-memory mode)
• APIs: Admin API, Client API (backend SDKs), Frontend API (edge-optimized)
• Metrics: Polling-based (SDKs report usage metrics periodically)

Feature Parity Analysis

Feature	GrowthBook	Unleash	Notes
Boolean flags	✅	✅	Core functionality solid in both
Typed values	✅	✅	GrowthBook: JSON primitives; Unleash: variants + payloads
A/B Testing	✅ Built-in	⚠️ Via Variants	GrowthBook native; Unleash variant system (less integrated)
Activation Strategies	⚠️ Limited	✅ Rich	Unleash: userId, % rollout, custom context
Analytics	✅ Native	⚠️ Basic metrics	GrowthBook: built-in results; Unleash: usage tracking only
Deno Support	✅ Tier-1	❌ NO OFFICIAL SDK	CRITICAL GAP
Payment Gating	⚠️ Some features	✅ None	Unleash fully open-source
Self-hosted Ease	✅ Lightweight (2GB)	✅ Standard (PostgreSQL required)	Both viable

Critical Blocker: Deno SDK

• Status: ❌ No official Deno SDK available
• Workaround: unleash-js-sdk via npm compatibility layer
• Risk: Untested in Deno edge environment; requires polyfills
• Decision: REQUIRES SPIKE VALIDATION BEFORE PROCEEDING

A/B Testing Consideration

• GrowthBook: Native experiments with automatic result tracking
• Unleash: Variant system (requires external analytics wiring)
• Impact: Current use (simple toggles) → ✅ fine; future AB testing → ⚠️ needs planning

Recommended Next Steps

Plan 1: Deno SDK Spike

Objective: Validate Unleash JS SDK compatibility with Deno/Danet runtime

Deliverables:

• Test harness: on-the-edge/tests/spike/unleash-deno.test.ts
• Decision document: on-the-edge/docs/unleash-decision.md
• Go/no-go recommendation with findings

Scope:

• Attempt import of unleash-js-sdk via Deno npm compatibility
• Create minimal test harness (isolated from Danet)
• Verify basic operations: initialization, flag evaluation, context updates
• Test storage polyfills (localStorage replacement for Deno)
• Document findings and blockers

Success Criteria:

• Test passes OR clear, specific blockers documented
• Runtime errors (if any) are understood
• Go/no-go decision made

Plan 2: Parallel Operation Adapter

Objective: Support both GrowthBook and Unleash SDKs simultaneously via adapter pattern

Scope:

• ExperimentAdapter interface (src/experiment/adapters/experiment.adapter.ts)
• GrowthBookAdapter wrapping existing logic
• UnleashAdapter integrating new SDK
• SDK selection via EXPERIMENT_PROVIDER env var
• Full unit test coverage

Deliverables:

• Adapter interface & implementations
• Updated ExperimentService (forwarding to adapter)
• Unit tests for both adapters
• Updated .env.example
• Migration documentation (docs/experiment-migration.md)

Benefits:

• Zero-downtime migration capability
• Per-environment SDK selection
• Validation period before full cutover
• Easy rollback if issues discovered

Timing: Post-spike validation (depends on Plan 1 success)

Deployment Context

Local-Stack infrastructure already provides:

• PostgreSQL (in infrastructure.yml) - required by Unleash
• Traefik routing (for admin UI + API)
• OTEL collectors (for observability)
• Redis (for future cache layer)

See local-stack infrastructure issue for full deployment plan.

Related Issues

• Local-Stack Unleash deployment: Infrastructure: Deploy Unleash feature flag platform local-stack#475

Open Questions

1. ✅ Deno SDK compatibility? → Requires spike
2. ✅ A/B testing expansion planned? → Affects migration strategy
3. ✅ Metrics/analytics integration? → May need external tooling with Unleash

Status

• Research: ✅ Complete
• Spike: ⏳ Pending (awaiting approval to proceed)
• Adapter: ⏳ Blocked on spike results
• Migration: ⏳ Blocked on adapter implementation

References

• Unleash Docs: https://docs.getunleash.io
• GrowthBook Docs: https://docs.growthbook.io
• Current GrowthBook setup: src/experiment/experiment.service.ts, src/middleware/growthbook.middleware.ts
• Experiment types: src/experiment/experiment.types.ts

[wax911]

Related Infrastructure Work

Local-Stack Deployment: AniTrend/local-stack#475

The infrastructure team is preparing the Unleash deployment in parallel with this investigation. This spike's go/no-go decision will unblock Plan 2 (adapter implementation) and Plan 3 (local-stack deployment).

Dependency Chain:

1. ✅ Research complete (this issue, linked infra issue)
2. ⏳ Spike validation → go/no-go decision (awaiting approval)
3. ⏳ Adapter implementation (5-7 days, post-spike)
4. ⏳ Infrastructure deployment (2-3 days, can run in parallel with adapter)
5. ⏳ Migration & validation (1+ week)