API Gateway Migration - Case Study

API Gateway Migration

Senior Backend Engineer · 2024 · 2 min read

Migrated 50+ microservices to a unified API gateway, reducing latency by 40% and improving developer experience

Overview

Led the migration from a legacy API gateway to a modern, high-performance solution that serves as the single entry point for all client requests

Problem

Our homegrown API gateway was becoming a bottleneck. It added 200-300ms of latency to every request, had limited observability, and required custom code for every new feature.

Constraints

  • Cannot break existing client integrations
  • Must migrate 50+ services without downtime
  • Limited budget for commercial solutions
  • 6-week timeline

Approach

Evaluated open-source and commercial API gateways, selected Kong for its performance and extensibility. Implemented a phased rollout using traffic splitting to gradually migrate services while monitoring for issues.

Key Decisions

Use Kong over AWS API Gateway

Reasoning:

Kong offers better performance, more flexibility, and avoids vendor lock-in. Self-hosting gives us full control over configuration and costs.

Alternatives considered:
  • AWS API Gateway
  • Nginx with custom Lua scripts
  • Envoy Proxy

Implement gradual traffic shifting with feature flags

Reasoning:

Allows us to test each service migration in production with real traffic before fully committing. Can instantly rollback if issues arise.

Tech Stack

  • Kong
  • Lua
  • PostgreSQL
  • Prometheus
  • Grafana
  • Kubernetes

Result & Impact

40% (from 250ms to 150ms p95)
Latency Reduction
52 services in 5 weeks
Services Migrated
No client-facing issues during migration
Zero Incidents

The new gateway has become a platform for cross-cutting concerns like rate limiting, authentication, and observability. Developer velocity has increased significantly.

Learnings

  • Traffic splitting is essential for safe migrations at scale
  • Investing in observability before migration pays off immediately
  • Plugin-based architecture makes it easy to add new capabilities

Migration Strategy

The phased rollout was critical to success. We started with low-traffic internal services to validate the approach, then gradually moved to higher-traffic customer-facing services.

Each service migration followed a checklist: update routing rules, enable traffic splitting at 1%, monitor for 24 hours, increase to 10%, 50%, then 100%. This gave us confidence at each step.

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