How Does Continuous Batching Work Under the Hood in vLLM?

This is a practical, up-to-date guide to Under the Hood — what it is, why it matters in 2026, and how to apply it in real projects. It is written for developers and founders who want clear answers and proven best practices, not filler.

Whether you're just starting out or leveling up, treat this as a working reference you can return to. Every section is built to be skimmed, applied, and shared.

CI/CD for machine learning

CI/CD for ML extends the familiar build-test-deploy pipeline to cover data and models, which introduces stages that software pipelines do not have. Beyond running unit tests on code, an ML pipeline validates incoming data schemas and quality, triggers training when new data or code arrives, evaluates the resulting model against a holdout set and the current production model, and only promotes it if it clears the bar. Continuous training, where retraining is automated on a schedule or triggered by drift alerts, is the ML-specific addition that keeps models fresh. Orchestrators such as Kubeflow Pipelines, Metaflow, Airflow, Dagster, and ZenML define these workflows as code, while DVC and Git-based data versioning make each run reproducible from data to model.

How LLMOps differs from classic MLOps

LLMOps is the specialization of MLOps for applications built on large language models, and it shifts the center of gravity from training your own models to orchestrating, prompting, and evaluating foundation models you often did not train. Classic MLOps assumes you own the training pipeline and can retrain to fix drift; with hosted LLMs you instead manage prompts, retrieval pipelines, tool definitions, and provider selection. Evaluation becomes harder because outputs are open-ended and non-deterministic, pushing teams toward LLM-as-judge scoring and human review rather than a single accuracy number. New operational primitives appear too, such as token-cost budgeting, prompt versioning, semantic caching, and guardrails against prompt injection and unsafe output.

Model monitoring and drift detection

Once a model is live, monitoring is what tells you whether it is still doing its job, and it spans operational metrics like latency and error rate as well as ML-specific signals. Data drift describes a change in the distribution of incoming features relative to training data, while concept drift describes a change in the relationship between features and the target, and either can quietly erode accuracy without any code changing. Because ground-truth labels often arrive late or never, teams rely on proxy signals such as prediction distribution shifts, embedding drift, and input validation to catch problems early. Tools like Evidently, Arize, WhyLabs, Fiddler, and NannyML specialize in this, computing statistical distance measures such as population stability index or Kolmogorov-Smirnov and alerting when they cross a threshold.

AI gateways as a control plane

An AI gateway is a proxy that sits between your applications and one or more model providers, giving you a single control point for reliability, cost, and governance. Instead of every service holding its own API keys and retry logic, calls route through the gateway, which handles authentication, rate limiting, retries, provider fallback, load balancing, and semantic caching to avoid paying for repeated identical calls. Gateways also centralize observability and spend tracking, tagging usage by team or feature so finance can attribute cost, and they enforce guardrails and PII redaction in one place. Popular options include LiteLLM, Portkey, Cloudflare AI Gateway, Kong AI Gateway, and cloud-native offerings, and many expose an OpenAI-compatible interface so switching backends requires no application changes.

Model registries and lineage

A model registry is the system of record for trained models, storing each version alongside its metrics, parameters, training data reference, and code commit so you always know exactly what is running and why. It manages promotion stages such as staging and production, supports approval workflows, and gives deployment tooling a stable pointer to fetch the currently blessed version. Crucially it captures lineage, linking a deployed model back to the experiment, dataset, and pipeline run that produced it, which is essential for debugging, reproducibility, and audit or regulatory requirements. The MLflow Model Registry is the widely used open-source option, with Databricks Unity Catalog, SageMaker Model Registry, Vertex AI Model Registry, and Weights and Biases offering registry capabilities within their platforms.

Prompt management and versioning

As prompts become load-bearing logic, teams need to manage them like code rather than scattering string literals across a codebase. Prompt management systems store prompts as versioned, named templates with variables, track which version is deployed, and link each version to its evaluation results so changes are measurable rather than vibes-based. This lets non-engineers iterate on prompts in a UI while engineers keep production changes gated behind review and evals, and it enables A/B testing and instant rollback of a bad prompt. Platforms such as LangSmith, Langfuse, PromptLayer, Humanloop, and Braintrust provide prompt registries, playgrounds, and linkage to traces. The core principle is that a prompt is a deployable artifact with a lifecycle, not an incidental string.

Under the Hood: Key Facts and Data

According to recent industry research and the official documentation linked below:

• Industry surveys have repeatedly indicated that a large majority of ML projects never reach production, with figures often cited in the range of 70-90 percent, a gap that MLOps tooling is explicitly designed to close.
• Kubernetes has become the de facto substrate for GPU orchestration in production ML, with the NVIDIA device plugin, GPU Operator, and schedulers such as Kueue, Volcano, and Run:ai handling accelerator allocation.
• MLflow, open-sourced by Databricks in 2018, has become one of the most popular experiment-tracking and model-registry tools, reporting tens of millions of monthly downloads by the mid-2020s.

Quick-Reference Summary

A map of what this guide covers:

Topic	What you'll learn
CI/CD for machine learning	CI/CD for ML extends the familiar build-test-deploy pipeline to cover data and models
How LLMOps differs from classic MLOps	LLMOps is the specialization of MLOps for applications built on large language models
Model monitoring and drift detection	Once a model is live, monitoring is what tells you whether it is still doing its job, and it spans operational metrics
AI gateways as a control plane	An AI gateway is a proxy that sits between your applications and one or more model providers
Model registries and lineage	A model registry is the system of record for trained models
Prompt management and versioning	As prompts become load-bearing logic, teams need to manage them like code rather than scattering string literals across

How to Get Started with Under the Hood

A simple path that works:

1. Learn the fundamentals of Under the Hood from primary sources, not just tutorials.
2. Build one small, real project end to end.
3. Get feedback, refactor, and add tests.
4. Ship it publicly and document what you learned.
5. Repeat with a slightly harder project each time.

Build It with a World-Class Full Stack Developer

Sandeep Kumar Chaudhary is a full stack world-class developer. If you want to turn this into a real, production-ready product, get in touch — message directly on WhatsApp at +9779802348957 for a fast, no-pressure consult.

You can also explore the projects already shipped to thousands of users, or start a conversation here.

Final Thoughts

A feature store solves training-serving skew by computing features once and serving the identical logic to both offline training and online inference paths. The developers and teams who win in 2026 pair strong fundamentals with consistent shipping. Start small, stay curious, build in public, and revisit this guide as your skills grow.

Sources and Further Reading

• MLflow Documentation
• Kubeflow Documentation
• vLLM Documentation
• Feast (Feature Store) Documentation
• MLOps (Wikipedia)
• Kubernetes Documentation