AI Gateway Buyer's Guide 2026 What to Actually Evaluate

The AI gateway market has filled up quickly. What started as a handful of open-source proxies is now a crowded field of hosted services, self-hostable platforms, and bolt-on features inside larger tools. Every one of them claims to route traffic, control cost, and improve reliability. For a team trying to choose, the marketing language blurs together, and it is easy to end up comparing demos instead of capabilities. The purpose of this guide is to give you a neutral evaluation framework, a checklist of criteria that matter in production, so that you can judge any gateway on its merits rather than on how polished its landing page is.

The criteria below apply to any gateway. For each one we describe what to look for and why it matters, and we use the AI gateway from TrueFoundry as one concrete illustration of what a given capability can look like in practice. Treat TrueFoundry here as a worked example, not a recommendation; the point is to show you what each criterion looks like when it is actually implemented, so you can ask the same questions of whatever you evaluate.

1. Provider and Model Coverage

The first question is simple: how many providers and models can the gateway reach, and how is that access exposed to your code? A gateway's whole value proposition rests on being able to add, swap, and compare models without touching application code, so breadth of coverage and a consistent interface are foundational.

What to look for: a single OpenAI-compatible endpoint that fronts a large catalog of models across many providers, so that your SDKs and tools work unchanged regardless of which model actually serves a request. Ask how new providers are added and whether that requires a gateway upgrade. As an illustration, TrueFoundry exposes one OpenAI-compatible schema across a catalog of a thousand-plus models; your code only ever sees the familiar chat-completions interface.

2. Routing and fallbacks
 

Coverage is only useful if you can control how traffic is distributed. Routing is where a gateway turns a list of models into a reliability and cost strategy.

What to look for: the ability to define a single logical model name that maps to multiple concrete targets, plus a choice of routing strategies, weight-based for gradual rollouts and load splitting, priority-based for ordered preference, and latency-based for performance. Equally important is failure handling: configurable retries, defined fallback conditions such as specific HTTP status codes, and automatic health-aware failover that shifts traffic off a degraded endpoint without application changes. Ask whether a routing change requires a redeploy; it should not. A gateway that offers only round-robin and no failover is doing a fraction of the job.

3. Cost controls and budgets

Because every request passes through the gateway, it is the natural place to measure and limit spend. This is often the criterion that justifies the whole project to finance.

What to look for: per-team, per-application, and per-environment cost attribution; the ability to set budgets and have the gateway enforce them; and rate limiting so that no single consumer can exhaust a shared quota or run up an unexpected bill. Ask whether cost data is real-time or reconciled after the fact, and whether limits are advisory or actually enforced in the request path. A gateway that only reports spend is weaker than one that can stop a runaway workload before the invoice grows.

4. Guardrails

The gateway is a chokepoint, which makes it the right place to enforce safety and data-protection policy on both the way in and the way out.

What to look for: the ability to screen inputs before a prompt leaves your environment and outputs before a response reaches a user, checking for sensitive data, policy violations, or disallowed content. Evaluate whether guardrails are configurable per route or per team, whether you can plug in your own checks, and what the latency impact is. Guardrails that only run on input, or that cannot be customized, limit how much of your policy you can actually enforce centrally.

5. Observability

You cannot operate what you cannot see. In a system where model calls fan out across providers, centralized observability is what turns the gateway from a black box into an instrument.

What to look for: detailed logging of requests and responses, token and cost metrics, latency and error-rate tracking, and, critically, telemetry in an open standard rather than a proprietary format. OpenTelemetry (OTel) support is the key criterion here, because it lets the gateway's data flow into whatever observability stack you already run instead of trapping it in a vendor dashboard. TrueFoundry, for example, emits OpenTelemetry-based observability, so traces and metrics land in your existing tooling. Ask whether you can export raw telemetry and correlate a gateway trace with the rest of your application traces.

6. Authentication and access control

A gateway concentrates access to expensive and sensitive resources, so its own access model has to be solid.

What to look for: distinct credential types for distinct uses, a personal access token for a developer working locally and a scoped application or virtual-account token for a deployed service, so that human and machine traffic can be governed and revoked independently. Beyond tokens, look for role-based access control (RBAC) that lets you say which teams can use which models and which policies apply to whom, enforced centrally. Ask how credentials to upstream providers are stored; ideally the gateway holds them so they are never copied into every application.

7. Deployment and data residency

Where the gateway runs, and where your data goes when it does, is often a hard requirement rather than a preference, especially under regulation.

What to look for: a range of deployment models to match your constraints. A fully hosted SaaS option for speed of adoption; a hybrid option where the provider operates the gateway but request and response data stays in your own object storage; and a self-hosted option that can run on-premises or fully air-gapped. Layer on regional routing and storage so that data stays in a required region, and ask how quickly a new region can be stood up. Compliance certifications, such as SOC 2, HIPAA, GDPR, and ITAR, are worth verifying directly rather than taking on trust, because they often gate whether you can route regulated data through the gateway at all.

8. Performance overhead

A gateway sits in the request path, so whatever latency it adds is paid on every call. This criterion is easy to overlook in a demo and painful to discover in production.

What to look for: a clear, published figure for added latency and a throughput number you can reason about, plus an architectural explanation of how those numbers are achieved. The strongest answer is an in-memory request path that avoids a per-request database or control-service call. As a concrete point of reference, TrueFoundry reports typical added latency under five milliseconds (internally around three to four), with roughly two hundred to two hundred fifty requests per second on a single CPU, because the component in the request path reads its configuration and cache from memory. Ask any vendor to explain not just their latency number but why it is what it is.

Turning the criteria into a scorecard

The eight criteria above form a checklist you can apply to any candidate. A practical approach is to score each one against your own requirements rather than in the abstract, because the right weighting depends on your situation. A small team optimizing spend will weight cost controls and provider coverage heavily; a regulated enterprise will treat deployment, data residency, and access control as non-negotiable gates before anything else is even considered.

• Provider coverage: One endpoint, broad catalog, easy to add providers.
• Routing and fallbacks: Multiple strategies, retries, automatic health-aware failover, no redeploy to change.
• Cost controls: Attribution, enforced budgets, rate limits, real-time visibility.
• Guardrails: Input and output screening, configurable, extensible.
• Observability: OpenTelemetry-based, exportable, correlatable.
• Auth and RBAC: Distinct token types, central role-based control, upstream credentials held by the gateway.
• Deployment and residency: SaaS, hybrid, self-hosted/air-gapped, regional routing, verified certifications.
• Performance: Published latency and throughput with an architectural reason behind them.

Run every candidate through the same eight questions and the comparison stops being about demos and starts being about fit.

Key Takeaways

• Evaluate gateways against a consistent framework rather than feature demos; the eight criteria here apply to any product.
• The foundational criteria are provider coverage and routing, because a gateway's core value is switching between models without touching application code.
• Cost controls, guardrails, observability, and access control are where a gateway either enforces policy or merely reports on it; prefer enforcement and open standards such as OpenTelemetry.
• Deployment model and data residency are often hard gates under regulation; verify certifications directly and check for SaaS, hybrid, and self-hosted or air-gapped options.
• Because a gateway sits in every request, insist on a published performance figure and an architectural explanation of how it is achieved.