The most common mistake is starting from the tool, not the process. The company buys a public API subscription or invests in GPUs without defining which business problem is being solved and how quality will be measured. The outcome is infrastructure without ROI and team frustration.
The second mistake is treating compliance as a late-stage activity. In many projects, data processing decisions are made quickly 'to launch the pilot', and only later does the legal team learn that customer data is flowing to a US-based provider without a proper DPA. Unwinding that situation is expensive and reputationally painful.
The third mistake is overestimating internal capability. Self-hosted LLM sounds attractive in a slide deck, but it requires mature MLOps. Without experience with vLLM, TensorRT, quantization, GPU scheduling and production serving, the environment will be either slow, expensive or unstable. A more honest decision is often to start in cloud and migrate selected workloads to on-premise only after capability is built.
The fourth mistake is the lack of an architect. Without someone owning horizontal decisions – model selection, orchestration layer, security boundaries, observability – the deployment becomes a sum of local choices without coherence. This is usually a longer project and a higher maintenance cost.
The fifth mistake is ignoring the model lifecycle. Open-weight models are released in new versions every few months. Without a re-evaluation process on the company corpus, the organisation stays on a model that was best on deployment day and is meaningfully worse a year later than available alternatives. This applies to both on-premise and cloud.