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Multi-tenant API Gateway

Go-based API gateway replacing an NGINX bottleneck. Per-tenant rate limits, OAuth2, and a single observable choke point.

Year 2024
Role Architect + senior engineer
Type Client engagement
Status Live

About this project.

A Go-based, observable API gateway built to replace an aging NGINX routing layer for a fintech platform.

Tech Stack

  • Go Gateway core
  • OAuth2 / mTLS Auth
  • OpenTelemetry Observability
  • Kubernetes Runtime

Project Info

Role
Architect + senior engineer
Timeline
2024
Client
Fintech platform (200+ enterprise customers)
Status
Live

Key Features

Per-tenant control

OAuth2 token introspection, per-tenant rate limits, quota enforcement, and request shaping.

Observable edge

End-to-end OpenTelemetry traces with per-route SLO dashboards and error budgets in Grafana.

Hardened

mTLS between gateway and upstreams, WAF rules per tenant tier, auto-revocation on compromised tokens.

Zero-downtime cutover

Shadow traffic mirroring for two weeks, per-route gradual rollout, rollback in under 60 seconds.

Smart routing

Weighted routing, canary splits, header-based experiments without redeploying upstream services.

Secrets discipline

Vault-issued short-lived credentials for upstream services, with rotation hooks and audit trail.

Feature set

Per-tenant control

  • OAuth2 token introspection
  • Per-tenant rate limits + quotas
  • Request shaping & rewriting

Observable

  • OpenTelemetry traces end-to-end
  • Per-route SLO dashboards
  • Error budgets surfaced in Grafana

Hardened edge

  • mTLS between gateway and upstreams
  • WAF rules tuned per tenant tier
  • Auto-revocation on compromised tokens

Zero-downtime cutover

  • Shadow traffic mirroring for 2 weeks
  • Per-route gradual rollout
  • Rollback in under 60 seconds

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