# FluidStack vs Union.ai

FluidStack records 154,620 monthly visits with +7.3% month-over-month growth and Paid, Contact for Pricing pricing. Union.ai records 17,787 monthly visits with -28.4% growth and Freemium, Contact for Pricing pricing.

| Metric | [FluidStack](https://openaitools.app/tool/fluidstack) | [Union.ai](https://openaitools.app/tool/union-cloud) |
| :--- | :--- | :--- |
| Website URL | https://fluidstack.io | https://union.ai |
| Categories | AI Developer Tools, AI Models, Large Language Models (LLMs) | AI Developer Tools, AI Workflow, Large Language Models (LLMs), AI Models |
| Pricing Model | Paid, Contact for Pricing | Freemium, Contact for Pricing |
| Monthly Visits | 154,620 | 17,787 |
| MoM Growth Rate | +7.3% | -28.4% |
| Primary Market | United States | United States |
| Direct Visits | 47,869 | 7,040 |
| Review Score | 4.4 | 4.4 |
| Saved Count | 1 | 0 |
| Supported Platforms | Website | Website |

## FluidStack

FluidStack is an AI compute provider that builds the physical layer underneath frontier model work: data centers, power, cooling and very large GPU clusters. Its public positioning is deliberately infrastructural rather than product-led — it describes building gigawatt-scale compute, bringing new sites online in months, and operating tens of millions of accelerators reliably. For teams training or serving large models, that translates into reserved, single-tenant-class capacity that is provisioned and operated for you rather than an instant, self-serve VM catalogue.

A distinguishing theme is the pairing of power and compute. FluidStack writes about redesigning compute and power infrastructure from first principles, developing off-grid solar to supply clusters, and using closed-loop cooling that fills tanks once and recirculates water indefinitely. It also emphasises building in the United States with onshored manufacturing, framing infrastructure ownership as a strategic question about which values shape the technology being built. For AI organisations, these are increasingly relevant because energy availability, not chip supply alone, is the binding constraint on scaling.

If you need a small number of GPUs for a day, FluidStack is probably not the fastest route; capacity is engaged at enterprise scale through a sales process. If you are planning a multi-month training run or a production inference fleet and want dedicated, purpose-built infrastructure with managed operations, it is a strong candidate to evaluate alongside the major hyperscalers and specialised GPU clouds.

**Pricing & Plans:** Enterprise and contact-for-pricing. FluidStack does not publish per-GPU-hour rates or a self-serve sign-up on its website; capacity is scoped and quoted through a direct sales conversation based on cluster size, duration and hardware. Catalogue listings classify it as a paid product requiring contact for pricing.

- **Datacenter-scale compute built in-house:** FluidStack designs and builds large AI data centers, including high-density campuses with significant per-site power capacity, rather than reselling capacity from other clouds.
- **GPU clusters for training and inference:** Clusters are architected for large-scale model training and inference, with high-bandwidth interconnect and orchestration suitable for distributed workloads.
- **Power and cooling engineered together:** The company develops off-grid solar and recirculating closed-loop cooling, treating power and water efficiency as core engineering problems.
- **Managed operations and reliability:** Smart hands, cluster provisioning and operations support let research teams focus on models while FluidStack runs the physical and orchestration layers.
- **US-built and onshored supply chain:** Data centers are built in the United States with onshored manufacturing of compute and power infrastructure, a deliberate supply-chain and sovereignty choice.

**Strengths:** Purpose-built AI infrastructure rather than generic cloud resale; Power, cooling and data center design handled in-house, which matters at scale; Managed provisioning and operations for large training and inference clusters; Explicit positioning on US-built, onshored infrastructure

**Limitations:** No published self-serve pricing or instant sign-up; access requires a sales conversation; Enterprise-scale focus means very small individual workloads may not be a fit; Capacity is concentrated in US locations, which may matter for latency-sensitive or data-residency-bound teams

[Profile (Markdown)](https://openaitools.app/tool/fluidstack.md)

## Union.ai

Union.ai grew out of the Flyte project, the open-source workflow engine used widely for data and ML pipelines, and it keeps that lineage in its design: you write ordinary Python tasks and task environments, and the runtime takes care of scheduling, caching, retries and typed data passing between steps. What Union adds on top is durability. If a run dies because a node disappears, a GPU is reclaimed, an API returns a 429 or an out-of-memory kill fires, the run is recovered and continues from the failed step rather than the beginning of the pipeline.

The current platform is organised around a handful of capabilities. The AI factory manages named, versioned artifacts so a checkpoint or dataset has a traceable producer and consumers, which matters for reproducibility. Production agents let teams keep the agent framework they already use, including OpenAI, Claude, PydanticAI and CrewAI, while making every turn of the loop durable, traced and sandboxed. The inference gateway puts external model APIs and self-hosted vLLM, SGLang or Ollama endpoints behind a single governed interface with virtual keys, budgets and guardrails. Around these sit scheduling primitives such as priority queues, concurrency limits, quotas and cluster selectors.

Deployment is deliberately bring-your-own-cloud. Union hosts the control plane, which stores references and metadata rather than payloads, while your data, models and compute stay inside your own perimeter, so your negotiated cloud rates and credits still apply. Union is available on AWS Marketplace and through self-service signup, with an optional managed-cluster service billed per cluster.

**Pricing & Plans:** Freemium-style entry with a free open-source Flyte option. The managed Team plan starts at a $950/month minimum, fully credited to usage, with the first month free and no card required at signup. Consumption is metered on actions, vCPU-hours, memory GB-hours and GPU-hours across published volume bands. Enterprise is custom-priced on an annual commit with volume discounts, and optional Union-managed clusters cost $500 per cluster per month, capped at $2,500.

- **Durable execution engine:** Tasks, traces and artifacts survive infrastructure failure. Runs fork, recover and replay from the last good step instead of starting over, with retries and caching handled by the runtime.
- **AI factory and artifact lineage:** Named, typed and versioned artifacts wire teams together, with lineage showing which run produced each version and which downstream tasks consume it.
- **Sovereign, bring-your-own-cloud deployment:** Run the control plane in Union's cloud while workloads execute on clusters in your AWS, GCP, Azure or neocloud account, under your own security perimeter.
- **Production agents and agent traceability:** Bring OpenAI, Claude, PydanticAI or CrewAI agents; each turn is traced and sandboxed in ephemeral containers, MCP servers and human approvals supported.
- **Inference gateway:** One gateway for hosted LLM providers and self-hosted vLLM, SGLang or Ollama endpoints, with virtual keys, budgets, guardrails and per-GPU observability.
- **Advanced scheduling and quotas:** Priority, concurrency, quotas and cluster selectors on queues, so backfills never steal capacity from production training or serving jobs.

**Strengths:** Durable execution means long training, inference and agent runs survive node loss, spot reclamation and API rate limits; Bring-your-own-cloud architecture keeps data, models and secrets inside your own security perimeter; Backed by the creators of Flyte, so the open-source engine and the managed platform evolve together; Transparent published rate card with marginal volume bands for actions, CPU, memory and GPU

**Limitations:** The Team plan carries a $950/month minimum that is only credited back as usage, so it is a poor fit for hobbyists or very small experiments; Because workloads run inside your own cloud, you still pay your cloud provider for compute on top of Union's metering; Setup expects a Kubernetes cluster and familiarity with Python task environments, which raises the bar for non-engineering users; Rate-card pricing across four meters (actions, vCPU, memory, GPU) can be hard to forecast without monitoring

[Profile (Markdown)](https://openaitools.app/tool/union-cloud.md)

## Frequently Asked Questions

### How do FluidStack and Union.ai compare in monthly traffic?

FluidStack has 154,620 monthly visits, while Union.ai has 17,787. Traffic estimates describe audience size, not product quality.

### How do their growth rates compare?

FluidStack has a month-over-month growth rate of +7.3%; Union.ai has -28.4%.

### How does pricing compare?

FluidStack: Paid, Contact for Pricing. Enterprise and contact-for-pricing. FluidStack does not publish per-GPU-hour rates or a self-serve sign-up on its website; capacity is scoped and quoted through a direct sales conversation based on cluster size, duration and hardware. Catalogue listings classify it as a paid product requiring contact for pricing. Union.ai: Freemium, Contact for Pricing. Freemium-style entry with a free open-source Flyte option. The managed Team plan starts at a $950/month minimum, fully credited to usage, with the first month free and no card required at signup. Consumption is metered on actions, vCPU-hours, memory GB-hours and GPU-hours across published volume bands. Enterprise is custom-priced on an annual commit with volume discounts, and optional Union-managed clusters cost $500 per cluster per month, capped at $2,500.

## Alternatives

| # | Tool Name | Monthly Visits | MoM Growth Rate | Pricing Model | Summary | Profile (Markdown) |
| :--- | :--- | :--- | :--- | :--- | :--- | :--- |
| 1 | [fal.ai](https://openaitools.app/tool/fal-ai) | 3,093,684 | -3.7% | Paid, pay-as-you-go usage-based pricing | Delivers developer-first serverless endpoints optimized for generative media models rather than general-purpose infrastructure. | [.md](https://openaitools.app/tool/fal-ai.md) |
| 2 | [RunPod](https://openaitools.app/tool/runpod) | 2,881,043 | +5.9% | Paid | The AI developer cloud for GPU pods, serverless inference and clustering | [.md](https://openaitools.app/tool/runpod.md) |
| 3 | [Together AI](https://openaitools.app/tool/together-ai) | 1,645,930 | +64.9% | Freemium, Paid | Together AI is the AI Native Cloud — a full-stack platform for running, fine-tuning and training open-source models. It spans serverless inference APIs, dedicated endpoints, GPU clusters, post-training and storage, all b | [.md](https://openaitools.app/tool/together-ai.md) |
| 4 | [Vast.ai](https://openaitools.app/tool/vast-ai) | 1,257,554 | +2.8% | Paid | Rent cloud GPUs by the second from a global marketplace | [.md](https://openaitools.app/tool/vast-ai.md) |
| 5 | [Modal](https://openaitools.app/tool/modal-com) | 1,196,021 | +30.2% | Freemium, Contact for Pricing | Serverless cloud infrastructure for AI and data workloads | [.md](https://openaitools.app/tool/modal-com.md) |
| 6 | [Nebius](https://openaitools.app/tool/nebius) | 1,145,711 | +10.7% | Paid, Contact for Pricing | An AI-native cloud built from silicon to API for training, tuning, and serving models | [.md](https://openaitools.app/tool/nebius.md) |
| 7 | [Salad](https://openaitools.app/tool/salad-gpu-cloud) | 713,519 | +10.4% | Free Trial, Paid, Contact for Pricing | Distributed GPU cloud that orchestrates the world's idle consumer GPUs | [.md](https://openaitools.app/tool/salad-gpu-cloud.md) |
| 8 | [Cerebras](https://openaitools.app/tool/cerebras) | 701,013 | -12.6% | Contact for Pricing | Utilizes proprietary wafer-scale processors for extreme training speeds, differing from standard NVIDIA GPU cluster setups. | [.md](https://openaitools.app/tool/cerebras.md) |
| 9 | [DeepInfra](https://openaitools.app/tool/deep-infra) | 457,810 | -8.9% | Paid | Specializes in cost-effective serverless API inference for open-weights models instead of raw infrastructure rentals. | [.md](https://openaitools.app/tool/deep-infra.md) |
| 10 | [Lightning AI](https://openaitools.app/tool/lightning-ai) | 272,562 | -12.3% | Freemium, Paid, Contact for Pricing | The AI cloud built by the creators of PyTorch Lightning | [.md](https://openaitools.app/tool/lightning-ai.md) |

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Source: https://openaitools.app/compare/fluidstack-vs-union-cloud

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