LLM Gateway

AssemblyAI's LLM Gateway is a routing layer designed specifically for Voice AI pipelines.

Reviewed by 7wData

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Publisher review

AssemblyAI's LLM Gateway is a routing layer designed specifically for Voice AI pipelines. It lets developers switch between more than 25 models across five providers—Anthropic, OpenAI, Google, Alibaba Cloud Qwen, and Moonshot AI Kimi—by changing a single line of code. The gateway runs inside the same infrastructure as AssemblyAI's transcription pipeline, which minimizes latency for voice-to-text-to-LLM workflows. It is built for engineering teams already using AssemblyAI's speech-to-text APIs who want to add LLM inference without managing multiple provider keys, rate limits, or retry logic. There is no no-code interface; using the gateway requires writing API calls.

The gateway automatically handles API keys, rate limits, retries, and fallbacks across providers. If one model returns an error or times out, the gateway routes the request to a configured fallback model without any client-side logic. It preserves context when routing to downstream models, so a conversation history or transcription output is passed through intact. The gateway uses pay-as-you-go pricing with zero markup on the underlying model costs—you pay exactly what the provider charges, plus AssemblyAI's standard API usage fees for the transcription side. The service supports both streaming and batch inference, though the streaming latency benefit is most pronounced when paired with AssemblyAI's realtime speech-to-text.

AssemblyAI's LLM Gateway competes directly with OpenRouter and LLM Gateway.io. OpenRouter offers a broader model catalog (200+ models) and a free tier, but it does not run inside a transcription pipeline, so voice-to-text-to-LLM workflows incur extra network hops. LLM Gateway.io provides self-hosted deployment options and enterprise compliance certifications, but it charges a per-request markup and does not include built-in speech-to-text. AssemblyAI's gateway is the only one that co-locates transcription and LLM inference in the same infrastructure, which reduces end-to-end latency for voice applications by an estimated 30-50% compared to routing through a separate gateway. However, it locks users into AssemblyAI's cloud—there is no self-hosted option for the gateway itself.

The primary trade-off is vendor lock-in: the gateway is tightly coupled to AssemblyAI's transcription pipeline, so moving to a different speech-to-text provider would require rebuilding the routing logic. There is no no-code interface, so non-technical users cannot configure model routing or fallbacks without developer support. On very large audio volumes, the cumulative cost of transcription plus LLM inference can ramp up quickly, even with zero markup on the model side. Finally, the gateway is entirely dependent on AssemblyAI's cloud infrastructure—any outage on their platform takes the gateway offline as well, unlike self-hosted alternatives that can run in your own VPC.

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How it works

  1. Multi-provider routing

    Routes requests across 25+ models from Anthropic, OpenAI, Google, Alibaba Cloud Qwen, and Moonshot AI Kimi.

  2. Automatic fallbacks

    If a model fails, the gateway automatically retries the request on a configured fallback model with no client-side logic.

  3. Zero markup pricing

    You pay the exact provider cost for each model call; AssemblyAI adds no per-request surcharge on the LLM side.

  4. Co-located infrastructure

    Runs inside the same infrastructure as AssemblyAI's transcription pipeline, reducing latency for voice-to-LLM workflows.

  5. Context preservation

    Passes conversation history or transcription output intact when routing to downstream models, maintaining continuity.

  6. Single-line model switch

    Developers can change the target model by altering one line of code, simplifying experimentation across providers.

  7. Pay-as-you-go billing

    No upfront commitments or tiered plans; you are billed based on actual usage of transcription and LLM inference.

Strengths and trade-offs

Strengths

  • Eliminates the complexity of managing multiple LLM provider API keys and rate limits for Voice AI pipelines.
  • Switches between any of 25+ models across five providers with a single line of code change, accelerating experimentation.
  • Automatically handles retries and fallbacks across providers, so a single failed model call does not break the entire request.
  • Runs inside the same infrastructure as AssemblyAI's transcription pipeline, minimizing end-to-end latency for voice applications.

Trade-offs

  • Requires developer skills to fully leverage the API; there is no no-code interface for configuring model routing or fallbacks.
  • No no-code interface exists, so non-technical users cannot set up or modify gateway behavior without engineering support.
  • Cost can ramp up on very large audio volumes because transcription and LLM inference are both billed per-request with no volume discounts.
  • Strong dependency on AssemblyAI's cloud infrastructure means any platform outage takes the gateway offline with no self-hosted fallback.

Pricing context

Pay-as-you-go with zero markup on LLM provider costs; you pay the exact model price plus AssemblyAI's standard transcription API fees. No free tier or volume discounts are mentioned.

Getting started with LLM Gateway

  1. Sign up for AssemblyAI

    Create an AssemblyAI account at their website. Complete the registration process and verify your email address. This account gives you access to both the transcription API and the LLM Gateway.

  2. Get your API key

    Log into your AssemblyAI dashboard and navigate to the API keys section. Generate a new API key and copy it. Store this key securely, as you will use it to authenticate all requests to the LLM Gateway.

  3. Configure model routing

    In your application code, set the target model by changing a single line. Specify the provider and model name (e.g., "anthropic/claude-3-opus"). Optionally define fallback models in case the primary model fails.

  4. Send a voice-to-LLM request

    Write an API call that sends audio data to AssemblyAI's transcription endpoint. The LLM Gateway automatically routes the transcribed text to your configured model. Include any conversation history or context in the request payload.

  5. Monitor usage and costs

    Use the AssemblyAI dashboard to track your API usage and billing. Review the number of transcription minutes and LLM inference calls. Adjust your model selections or fallback rules to optimize cost and performance.

Frequently Asked Questions

What is AssemblyAI's LLM Gateway?

AssemblyAI's LLM Gateway is a routing layer for Voice AI pipelines that lets developers switch between over 25 models from five providers by changing a single line of code, while automatically handling API keys, rate limits, and retries.

How does LLM Gateway reduce latency for voice applications?

The gateway runs inside the same infrastructure as AssemblyAI's transcription pipeline, eliminating extra network hops. This co-location reduces end-to-end latency for voice-to-text-to-LLM workflows by an estimated 30-50% compared to routing through a separate gateway.

What pricing model does AssemblyAI's LLM Gateway use?

It uses pay-as-you-go pricing with zero markup on underlying model costs. You pay exactly what the provider charges for each LLM call, plus AssemblyAI's standard API usage fees for transcription. No free tier or volume discounts are mentioned.

How does LLM Gateway compare to OpenRouter and LLM Gateway.io?

OpenRouter offers more models and a free tier but adds network hops for voice workflows. LLM Gateway.io provides self-hosted options and compliance certifications but charges per-request markup and lacks built-in speech-to-text. AssemblyAI's gateway co-locates transcription and LLM inference for lower latency.

What are the main drawbacks of using AssemblyAI's LLM Gateway?

The gateway is tightly coupled to AssemblyAI's transcription pipeline, creating vendor lock-in. There is no no-code interface, so non-technical users cannot configure routing without developer support. Costs can ramp up on large audio volumes, and any platform outage takes the gateway offline.

Does LLM Gateway support streaming inference for voice AI?

Yes, the gateway supports both streaming and batch inference. The streaming latency benefit is most pronounced when paired with AssemblyAI's realtime speech-to-text, as the co-located infrastructure minimizes delays for voice-to-LLM workflows.

Alternatives

How LLM Gateway compares

Direct head-to-head against 3 competitors. Picked by 7wData.

This tool

LLM Gateway

Pricing
Pay-as-you-go with zero markup on LLM provider costs; you pay the exact model price plus AssemblyAI's standard transcription API fees. No free tier or volume discounts are mentioned.
Target
AssemblyAI's LLM Gateway is a routing layer designed specifically for Voice AI pipelines.
Strength
Eliminates the complexity of managing multiple LLM provider API keys and rate limits for Voice AI pipelines.
Watch for
Requires developer skills to fully leverage the API; there is no no-code interface for configuring model routing or fallbacks.

OpenRouter

Pricing
5% markup on requests; no self-hosting tier
Target
Quick prototyping for small projects
Deployment
Cloud only
Strength
Passthrough billing with easy setup for non-technical users
Watch for
5% markup on all requests; no custom model support

Portkey

Pricing
Custom/Contact sales; no free tier
Target
Development teams needing enterprise security
Deployment
Cloud; self-hosted available
Strength
Advanced guardrails and enterprise governance features
Watch for
Acquired by Palo Alto Networks; steep learning curve and limited scalability

LiteLLM

Pricing
Open source (free); paid cloud tier available
Target
Engineering teams building custom LLM infrastructure
Deployment
Self-hosted or cloud
Strength
Open-source extensibility with support for 1600+ LLMs
Watch for
Each request adds >50ms latency; highly technical setup required

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Sources

Reporting on this tool draws on these publicly available sources.

  1. www.linkedin.com
  2. www.assemblyai.com
  3. www.assemblyai.com
  4. www.assemblyai.com