What is the difference between blue-green and canary deployment?

A blue-green deployment runs two parallel environments and flips all traffic at once. A canary deployment runs a small percentage of traffic on the new version while the bulk of traffic remains on the current version, with the percentage ramping up as confidence grows. Blue-green is faster to cutover and to revert. Canary is lower-risk on the cutover because only a fraction of traffic hits the new version at any time. AI gateways benefit from canary for routing changes and from blue-green for full version upgrades.

How long should blue stay running after the cutover?

The retention window is the holding period during which a fast revert is possible. Typical windows are 24 hours for behavioral changes and 7 days for major version upgrades. The window has to be long enough that latent issues in the new version surface in the production traffic mix, but short enough that the cost of running two environments is bounded. The window can be extended if the monitoring suggests caution.

Does blue-green deployment work with stateful AI gateways?

Stateful AI gateways introduce complexity because the in-memory state of the blue gateway is not transferred to green at the cutover. The cutover loses any per-request context that was held in memory. Stateless gateways, where every request is processed without reliance on prior request state, are the natural fit for blue-green deployment.

What is shadow traffic?

Shadow traffic is a copy of live production requests that is replayed against the green environment in parallel with the request being served by blue. The shadow request does not affect the production response that the caller receives. The shadow response is compared against the production response to detect divergences before the cutover. Shadow traffic is the verification gate that catches the most production-realistic issues.

How does blue-green deployment interact with rate limits?

Rate limits that are tracked per-deployer or per-identity have to use a shared counter store across blue and green. If each environment maintains its own counter, the cutover doubles the effective limit for the cutover window (the caller has one counter on blue and another on green, both at zero). The shared counter store keeps the limit accurate across environments.

Can a blue-green deployment span multiple regions?

A multi-region blue-green deployment treats each region's environment pair as a unit and cuts over regions in sequence. The first region cuts over and is observed for a holding period. If stable, the second region cuts over. The pattern is slower than a single-region cutover but reduces the blast radius of a bad deployment to one region at a time.

AI Gateway Blue-Green Deployment: How to Ship a Gateway Version Without Cutting Traffic

A blue-green deployment runs two full gateway environments in parallel. The current production environment (blue) continues to serve traffic. A new environment (green) is built, configured, and verified independently. At the cutover, traffic flips from blue to green at the load balancer. Blue stays warm in case a fast revert is needed. The pattern has been standard practice for web infrastructure for a decade. The AI gateway version of the pattern has two differences from a generic API gateway. The policy and routing state has to be consistent across the cutover. The audit log chain has to remain unbroken.

I want to walk through the blue-green pattern at the AI gateway layer, the state-consistency requirements that change the design, the verification gates that run before the cutover, and the fallback path that preserves audit continuity.

What a blue-green AI gateway deployment looks like

A blue-green AI gateway deployment has six phases.

Phase 1: Provision green. The new environment is provisioned with the new gateway version, the new dependencies, the new infrastructure configuration. The green environment is fully isolated from blue at the compute and storage layers; the two environments do not share gateway state.

Phase 2: Synchronize state. The policy registry, the routing rules, the identity store, and the secrets are synchronized from blue to green. The audit log destination is configured to the same store that blue is writing to, so that the audit chain continues across the cutover.

Phase 3: Verify green. The green environment is exercised against a synthetic traffic suite that covers the policy domains, the routing scenarios, the error paths, and the audit-log writes. The verification confirms that green behaves identically to blue on the synthetic suite.

Phase 4: Cutover. The load balancer flips traffic from blue to green. The cutover is atomic at the load balancer layer. Blue continues to run but receives no new requests.

Phase 5: Monitor. The first 15 to 60 minutes after cutover are the high-attention window. Error rates, latency, policy denial rates, and audit-write success rates are monitored. The monitoring compares green against the blue baseline from the same time window the prior day.

Phase 6: Decommission or revert. If the green environment is performing as expected, blue is decommissioned after a holding period (typically 24 hours). If green is misbehaving, traffic flips back to blue at the load balancer and green is investigated.

The state-consistency requirements that change the design

Three state categories have to be consistent across the blue-green cutover.

Policy state. The policy versions, the active pointers per policy domain, and any policy-derived caches. The synchronization runs from the policy registry, which is the authoritative store. The registry is shared between blue and green so the cutover does not change which policy version is active.

Routing state. The routing rules, the model destination configurations, the canary percentages if any are in effect. The routing state similarly synchronizes from a shared configuration store. A blue-green cutover should not flip an in-progress routing canary into an inconsistent state.

Identity context. The identity provider configuration, the JWT signing keys, the token validation rules. The identity context is shared because both blue and green have to validate tokens from the same identity provider against the same trust chain.

The shared state stores are the architectural requirement. A gateway design that keeps policy and routing state inside the gateway runtime makes blue-green deployment difficult because the two environments diverge as soon as policy or routing changes. A gateway design that externalizes state to a registry or configuration store keeps blue and green consistent.

The audit log chain across the cutover

The audit log is the historical record. Every gateway request produces a signed audit entry. The signatures form a chain such that any modification to a historical entry is detectable. The blue-green cutover passes between two gateway instances, and the audit chain has to span the transition without gap or break.

Three properties have to hold.

Property 1: The signing keys are shared. Blue and green both sign audit entries with the same key. The verification of any historical entry succeeds regardless of which environment wrote it.

Property 2: The log destination is shared. Both environments write to the same log store. The store maintains the ordering of entries by timestamp and sequence number. The audit query against the store returns entries from both environments interleaved by timestamp.

Property 3: The sequence numbering is coherent. If audit entries carry a monotonic sequence number, the sequence has to advance correctly across the cutover. The shared store typically owns the sequence allocation so that both environments see the same view.

A blue-green deployment that does not satisfy all three properties produces audit gaps or audit-chain breaks at the cutover boundary. The supervisory authority that comes back six months later and queries the period around the cutover sees the gap. The remediation cost of an audit-chain break is high. The deployment design has to avoid it.

The verification gates that run before the cutover

The verification is the difference between a low-risk and a high-risk cutover. A blue-green deployment that flips traffic before verification is a worse pattern than a slow rolling update, because the entire request surface flips at once.

A defensible verification stack runs four gates.

Gate 1: Synthetic traffic suite. The green environment is exercised against a synthetic suite of requests that covers the policy domains, the routing scenarios, the data classes, and the error paths. The suite is built from production-derived traffic patterns with sensitive fields redacted. Pass criterion: synthetic responses on green match the responses blue produces for the same inputs.

Gate 2: Audit write verification. For every synthetic request, the audit entry is checked against the expected schema and the signing chain is verified. Pass criterion: 100 percent of synthetic requests produce a valid audit entry on green.

Gate 3: Latency and error parity. The green environment's latency distribution and error rate are compared against blue's baseline. Pass criterion: green is within an acceptable band of blue (typically within 10 percent of blue's p99 latency and within 0.1 percent of blue's error rate).

Gate 4: Shadow traffic comparison. A copy of live production traffic is replayed against green without affecting production responses. The two responses are compared. Pass criterion: green's responses are functionally equivalent to blue's, with any differences explained and accepted.

All four gates have to pass before the cutover proceeds. A gate failure routes the green environment back to investigation.

The fallback path

The fallback is the move back to blue when green misbehaves after cutover. The fallback has to be fast and has to preserve audit integrity.

The fast property requires that blue remains running and configured for traffic during the post-cutover monitoring window. The load balancer's flip from green back to blue takes seconds. The configuration to support fast fallback adds the cost of running both environments in parallel for the monitoring window, but the cost is justified by the recovery time.

The audit-integrity property requires that the audit entries written by green during the period before the fallback remain in the shared store. The fallback does not roll back the audit log because the audit log is the record of what actually happened. The audit log shows green operating during a window, then blue resuming. The supervisory authority's query against that period returns the correct picture of the events.

DeepInspect

DeepInspect is a stateless policy gateway between authenticated users or agents and any LLM. The gateway is designed for parallel-environment deployment. Policy state, routing state, identity state, and audit destination are externalized to shared stores. Blue and green environments share the audit signing key and the log destination, so the audit chain remains unbroken across cutovers.

For an operations team running blue-green deployments at the AI gateway layer, DeepInspect provides the architecture the pattern requires. The verification suite runs against the green environment with full audit-write checks. The fallback path retains audit continuity. The decommissioning of blue happens only after the monitoring window confirms green is stable.

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