A structured examination of code review approaches across two dimensions: timing (synchronous vs. asynchronous) and impact (blocking vs. non-blocking). Covers pair/ensemble programming, pull requests, ad-hoc consultations, and post-push reviews with Trunk-Based Development. Each approach is analyzed for its trade-offs in velocity, quality, knowledge sharing, and team structure fit. Concludes that no single approach is universally optimal — teams should choose based on project criticality, team structure, and engineering maturity, and evolve their strategy over time.