Context Lake in Practice: Detecting fraud with live-context LLMs

Written by
Boyd Stowe
Published on
September 9, 2025

A Real-World Story: Fraud in the Milliseconds

On a Tuesday morning, a credit card processor notices a wave of suspicious activity. Dozens of small charges are being tested against stolen cards. Each charge is only a few dollars, but within minutes the fraud could scale into thousands in losses if not stopped immediately.

Predictive AI is commonly used to detect fraud in almost every financial institution, but that is limited to a small set of very defined use cases on discrete sessions. Cross session analysis, which is very computationally intensive, has been very difficult to do before the advent of hosted Generative AI models. Using a self-hosted AI Agent, this can now be achieved.

With every transaction the model is asked a simple question: “Is this suspicious?” On its own, the model cannot know. Its training data is frozen months in the past and does not contain these card numbers, merchant IDs, or devices. What matters is not the training set but the live context. Were there other transactions seconds ago from the same IP address? Did the same device issue repeated charges against different accounts? If the system can answer these questions in real time, the cross-session fraud can be stopped as it happens. If not, the opportunity is gone.

Why Multi-Tool Stacks Fail in Production

If you’ve ever tried to build a real-time Generative AI system, the architecture will feel familiar. Transactions go into Postgres or MySQL. Streams run through Kafka or Flink. Analytics land in Snowflake or BigQuery. Embeddings are generated asynchronously and pushed into Pinecone or Weaviate then the hosted Generative AI model api is called. Logs are dumped into Elastic or OpenSearch. On paper, each tool is “best-in-class.” In code, it quickly becomes a mess.

  • Latency shows up first. You write an orchestration layer — maybe with LangChain, maybe custom code — that has to fan out queries across half a dozen systems. Postgres can answer fast, but Snowflake takes longer, and embeddings add another call. By the time you merge results, hundreds of milliseconds have passed. For fraud detection, that’s already too late.
  • Data drift is constant. You wire up Kafka to replicate streams, but jobs fail, lags creep in, and batch windows mean analytics are always a few minutes old. You add retries and monitoring, but the reality is your AI is making “real-time” decisions on data that isn’t.
  • Glue code becomes its own product. You’re maintaining schema mappings between Postgres and Snowflake, transformation logic in Flink, indexers for Pinecone, and ETL scripts for Elastic. None of this is core to your fraud detection use case, but it eats the majority of your engineering hours.
  • Fragility is baked in. When one system lags or fails, the whole pipeline drifts apart. You end up debugging Kafka offsets at 2 a.m. or chasing down why embeddings are stale. The orchestration layer can hide this in a demo, but in production it only amplifies the brittleness.

For a developer, the pain is obvious: you’re not building fraud detection, you’re building plumbing. And the more plumbing you add, the less you trust the system to stop fraud in the milliseconds where it matters.

For the business, complexity is an unavoidable complication. Each of these systems has to be scaled, tuned, and monitored independently. Engineers must manage schema drift across databases, model drift across ml algorithms, job failures in pipelines, and synchronization between stores. Glue code becomes as large as the AI itself. The operational burden grows with every new feature, turning data freshness into a moving target rather than a guarantee.  

Fragility is inherent. The more moving parts in the system, the more ways it can fail. If Pinecone is slow, embeddings cannot be retrieved. If Snowflake lags, aggregates are out of date. If a Kafka job crashes, downstream systems silently drift apart. Orchestration frameworks attempt to mask these failures but often become bottlenecks themselves. The architecture may function in controlled demos, but in live environments it struggles to deliver.  

This also leads to feature and product lock in. Changing the system even just to patch one aspect can cause a chain reaction of failures that are difficult to recover from so ‘CHANGE NOTHING’ becomes the mantra. In the high-tech world, if you are standing still, you are falling behind. Soon your more agile competitor is beating you at every turn.

From Fragile Stacks to a Context Lake

At some point, every engineer working on these systems has the same thought: “Why am I gluing five databases together just to answer one question?” You don’t actually care whether the answer comes from Postgres, Snowflake, or Pinecone. You care that when the model asks “Is this suspicious?”, it can see everything that matters — the transactions, the device, the IP address, the past history — instantly and in context.

That’s what a context lake gives you: one system designed to handle transactional events, time-series streams, logs, and embeddings in the same place, without fragile pipelines in between. Instead of juggling sync jobs, you get a single query layer where all the context is already fresh and aligned.

From a developer’s seat, the benefits are immediate:

  • No orchestration gymnastics. You don’t have to fan out queries across five APIs and stitch the results back together. One query gets you relational data, vector similarity, and time-series stats side by side.
  • Freshness by default. You stop worrying about Kafka lag or Snowflake batch windows. Events stream in once, and the context is instantly queryable without waiting for downstream jobs to catch up.
  • Less plumbing, more product. Instead of spending cycles maintaining fragile ETL pipelines and indexers, you spend them refining your detection logic or training better models.
  • Predictable performance. Because you’re not hopping across systems with different latency profiles, you can trust that queries will stay in the millisecond range — the difference between catching fraud live and reading about it in a postmortem.

For the developer, the shift is subtle but huge: you’re no longer building duct tape pipelines that simulate “real-time AI.” You’re actually giving the model live context at the moment it needs it. The system moves from demo-ready to production-grade.

Great — here’s how we can extend the developer-perspective section with a concrete, dev-facing fraud detection flow. I’ll keep it practical, like something you’d actually sketch out when evaluating a system:

A Developer’s View: Fraud Detection in a Context Lake

Here’s what it looks like in practice. In the old stack, you’d be juggling queries across Postgres, Kafka, Snowflake, and Pinecone just to answer a simple fraud question. In a context lake, it’s one query.

Say a new transaction comes in:

{
 "card_id": "1234-5678-9012-3456",
 "amount": 4.99,
 "merchant_id": "M-482",
 "device_id": "D-991",
 "ip_address": "10.42.0.88",
 "timestamp": "2025-08-27T13:22:01Z"
}

Instead of firing off five lookups, you write a single query:

SELECT  t.card_id,
COUNT(*) FILTER (WHERE t.timestamp > now() - interval '60 seconds'
AND t.ip_address = '10.42.0.88') AS recent_ip_activity,
COUNT(*) FILTER (WHERE t.timestamp > now() - interval '60 seconds'
AND t.device_id = 'D-991') AS recent_device_activity,
VECTOR_SIMILARITY(t.embedding, $suspicious_patterns) AS anomaly_score
FROM transactions t
WHERE t.card_id = '1234-5678-9012-3456'
OR t.device_id = 'D-991'
OR t.ip_address = '10.42.0.88';

 

One query does three things at once:

  1. Pulls relational history for the card, IP, and device.
  1. Counts recent bursts of activity (time-series).
  1. Runs a vector similarity check against known fraud patterns.

All of it happens in milliseconds because the context lake holds the rows, the events, and the embeddings in the same system. No Kafka lag, no Snowflake delay, no Pinecone async jobs.

The output might look like this:

{
 "card_id": "1234-5678-9012-3456",
 "recent_ip_activity": 14,
 "recent_device_activity": 22,
 "anomaly_score": 0.91
}

 

From here, the fraud agent has live context:

  • The number of sessions from the same IP in the last minute.
  • The number of charges per device on the same device.

Answering “Is this transaction suspicious?” becomes trivial — because the system surfaces the right context in real time. This is just one example with numeric examples. The context could literally be anything that can be sent to the AI Agent for it to infer whether any combination of context inputs could constitute fraud.

The Bigger Picture

Fraud prevention is only one domain where Tacnode changes what is possible. In customer support, the Context Lake holds account histories, tickets, and knowledge base articles in one place, allowing an AI agent to deliver responses that are both personalized and current. In compliance, Tacnode ingests regulatory updates and contract changes as they occur, ensuring legal copilots query the most up-to-date information rather than stale indexes. In each case, the story is the same: stitched-together toolchains introduce latency, staleness, and fragility, while Tacnode provides a single, real-time substrate where models can retrieve truth at inference.

Takeaway

Generative AI cannot succeed in production on the strength of models alone. Without real-time context, answers remain brittle, generic, and untrustworthy. Multi-tool stacks try to provide context by piecing together databases, warehouses, and vector stores, but the result is latency, complexity, and staleness. Tacnode replaces that patchwork with a Context Lake: one system that ingests continuously, stores flexibly, and retrieves instantly.

If the goal is AI that is accurate, personalized, and grounded in live reality, Tacnode is the architecture that makes it possible.