learn-ai-infra-with-phoebe / Practitioner session 1 of 10
Learn AI Infra with Phoebe · Practitioner track · Session 1 of 10

Eight layers, five personas

A data platform is not a product you buy. It is eight layers, each one unblocking a specific person to do a specific job, each one costing real money, and each one holding a chokepoint where truth gets decided. Tonight you build the whole thing in your browser and watch two things move together: who can work, and what the bill says. Then you break it the way most organizations break it - by buying the last layer first.

🟢 Practitioner track Platform · DE · architects Vendor-neutral · real rate cards Start here
0-3 · Welcome 3-18 · The layers, the personas, the chokepoints 18-42 · Build-along: climb the stack, then break it 42-45 · Q&A
Part 0

How this track works

Ten sessions, one deliverable: a reference architecture for your organization's five data personas - data engineer, analyst, data scientist, AI engineer, and the business client who just wants an answer. This is not a vendor tour. Each session takes one layer, states the job it does, names the real options with honest cost bands, and identifies the chokepoint - the narrow waist where that layer's truth is decided and where lock-in actually lives. b2 through b8 walk the stack bottom to top; b9 is the evidence session on self-serve; b10 assembles and costs your architecture. Every price on these pages was fetched from a vendor's own billing feed with the date attached, because this subject goes stale faster than anything else on the shelf.

Live - presented in session Self-study - read after class ▶ Live platform sim - real rate-card arithmetic Official sources covered
★ What you walk out with today The eight layers in order, the five personas and exactly which layers each one needs, the chokepoint idea that makes the whole stack legible, and the sequencing rule this course exists to teach: self-serve is layer eight, and buying it first is the most expensive mistake in enterprise data.
Part 1 · the map of the whole course

The stack, bottom to top 8 min live

Every enterprise data platform, whatever the logos on it, is these eight jobs. Not eight products - eight jobs, some of which one product may cover and some of which need three. Learn the jobs and the vendor landscape stops being intimidating, because every pitch you ever hear is a claim about which of these eight boxes a product fills.

8 · Self-serve + governance talk-to-data, permissions, lineage, cost attribution unblocks: business clients 7 · LLM gateway + app runtime routing, cost control, caching, observability unblocks: AI engineers 6 · Compute + MLOps train, register, deploy, monitor, CI/CD unblocks: data scientists 5 · Semantic layer + BI agreed metrics, dashboards, reports unblocks: analysts 4 · Lakehouse engine + transform SQL at scale, modelled marts 3 · Ingestion + orchestration data arrives reliably, on schedule, observably unblocks: data engineers 2 · Table format + catalog ACID and one source of truth on object storage 1 · Storage cheap durable bytes in open formats layers 1-2 unblock nobody on their own - and skipping them breaks everything above
🔍 Click to zoom - eight jobs, and who each one lets go to work
LiveReading the stack in both directions4 min▶

Read it bottom-up and it is a dependency chain: nothing above works without the layers beneath it. Read it top-down and it is a list of business outcomes, which is how it gets funded. Most platform failures come from an organization funding top-down and building top-down at the same time - buying the outcome without the dependencies.

Two observations that will keep recurring:

  • Layers 1 and 2 unblock nobody by themselves. Nobody's job title is "uses the object store." That makes them the easiest layers to underfund and the most expensive to retrofit.
  • The gap between layers 4 and 5 is where most organizations actually live. Data lands, SQL runs, and every dashboard defines revenue slightly differently. That is not a tooling problem, it is a missing layer.
Real world

Airbnb published this exact progression over six years. Dataportal in 2017 solved discovery ("where is the data?"). Minerva in 2021 solved metric definitions - 12,000+ metrics, 4,000+ dimensions, 200+ data producers - because teams kept reporting conflicting numbers for the same question. Metis in 2023 added governance and lineage, with a graph of 100M+ nodes and 300M+ edges serving 1,000+ weekly users. Three artifacts, one company, published on their own engineering blog. Nobody starts with layer 8.

Self-studyWhy "just buy a platform" does not collapse the list3 min read▶

Databricks, Snowflake and Microsoft Fabric all sell something they call a unified platform - and all three genuinely cover several of these layers. But read their own words and they are unifying different axes:

  • Databricks unifies workloads - BI and ML on one copy of the data.
  • Microsoft Fabric unifies organizational storage - one OneLake per tenant, and their docs are blunt about it: "You can't delete OneLake or create multiple OneLakes."
  • Snowflake unifies workload types including transactional - running OLTP alongside analytics.

The right question in any evaluation is not "is this platform unified?" but "which axis does my actual pain sit on?" A team drowning in duplicate departmental lakes has a different problem from a team whose ML and BI numbers disagree, and the two buy differently.

Part 2 · the idea that makes the stack legible

Every layer has a chokepoint 7 min live

Here is the frame that turns eight disconnected topics into one course. In every layer there is a narrow waist - a single place where plural, messy inputs become a singular, consequential output. That waist is where truth gets decided, where governance is possible, and where lock-in actually lives. Learn to find it, and you can evaluate any product in the category in about ten minutes.

LayerThe chokepointWhat it decides
Storageegress economics and retention termswhat it costs to read your own data, and whether you can leave
Table format + catalogthe catalogaccess control, credential vending, commit sequencing
Orchestrationthe asset graphwhat "this ran successfully" actually means
Enginethe compute contractwho pays for a badly written query
Semantic layermetric definitionswhat "revenue" means, everywhere
MLOpsthe model registrywhat is in production and how to roll it back
LLM gatewaythe gatewaywhich models run, at what cost, with what audit trail
Self-servethe semantic layer, againwhether an answer can be trusted
LiveThe chokepoint test: is it the only door?4 min▶

A chokepoint only governs if it cannot be bypassed. This is the single most useful evaluation question in the course, and it applies to every layer:

  • A model registry that developers can route around by deploying an artifact straight from object storage provides zero governance, regardless of how good its UI is.
  • A semantic layer that analysts can bypass by writing raw SQL in the BI tool defines metrics for exactly the people who were already following the rules.
  • An LLM gateway that teams can skip by calling the provider API directly gives you cost dashboards covering the compliant half of your spend.

So when a vendor demos a governance feature, ask the same question every time: what stops someone from going around this? If the answer is "policy" rather than "architecture," you do not have a chokepoint - you have a suggestion.

Self-studyThe same pattern twice: registry and gateway3 min read▶

Notice something in the table above: layers 6 and 7 have structurally identical chokepoints. The model registry is the narrow waist for models you train; the AI gateway is the narrow waist for models you rent. Both answer exactly the same four questions:

  • What is running in production right now?
  • Where did it come from?
  • Who approved it?
  • How do I roll it back?

The strongest evidence that these are one pattern and not two: MLflow, the canonical MLOps tool, now ships an AI gateway. Same team, same governance instinct, applied to a new era of models. If you understand b7, b8 is half-learned already.

Demo 1 of 2

Climb the stack, watch the personas wake up ★ 14 min · everyone runs it

Below is your platform, empty. Switch on one layer at a time, bottom to top, and watch two numbers move together: how many of your five people can actually do their job, and what the bill says. Every dollar is computed live from published rate cards fetched on 6-7 August 2026 - AWS S3 storage and egress tiers, AWS p5 three-year reserved GPU pricing, NVIDIA AI Enterprise per-installed-GPU list price.

Nothing on: $0, and all five people are blocked. Obvious, but note who is blocked and why - each card names the specific job they cannot do.

+ Storage, + Catalog: $1,578/month, and still zero personas unblocked. Two layers of spend with nobody's job improved yet. This is the stretch that gets cut in budget reviews, and cutting it is why the layers above later fail.

+ Orchestration: $2,178, and your data engineer starts working - first person unblocked, three layers in.

+ Engine, + Semantic layer: $5,878, analyst unblocked. Note the analyst needed five layers, not one BI licence.

+ MLOps: $9,395, data scientist unblocked - and watch the jump. This is the most expensive single layer, and most of it is GPU compute and per-installed-GPU licensing (b7 breaks that bill down).

+ Gateway, + Self-serve: $11,295/month, $135,540/year, all five working. Sit with that number - it is the honest price of the platform your organization keeps describing as "just a dashboard tool."

Climb the stack and two numbers move together MONTHLY BILL, LIVE FROM PUBLISHED RATE CARDS UNBLOCKED OF 5 nothing on $0 storage + catalog $1,578 + orchestration $2,178 + engine + semantic $5,878 + MLOps $9,395 + gateway + self-serve $11,295 $135,540 a year with all eight on - the honest price of "just a dashboard tool." MLOps is the biggest single jump: GPU compute plus per-installed-GPU licensing (b7).
🔍 Click to zoom - two layers and $1,578 a month buy nobody a working day
What this model is and is not The cost arithmetic is real and recomputes live from published rate cards. The persona outcomes are a teaching model, not a simulation of your organization - your team sizes, volumes and existing contracts will move every number. What transfers is the shape: the order of unblocking, and how much you spend before anyone notices a difference.
Demo 2 of 2

Now break it the way real organizations do ★ 10 min · everyone runs it

With all eight layers on, switch off the semantic layer and watch the business-client card. They stay unblocked - the self-serve tool still answers - but the card turns red. That is not a bug in the simulator. That is the single most common failure in enterprise data, rendered honestly.

Turn Semantic layer + BI off while Self-serve stays on. The client card reads: "Answering confidently from ungoverned metrics - plausible SQL, wrong business logic." They are not blocked. They are getting answers. The answers are just not trustworthy.

Read the verdict line and the number in it: Microsoft's engineering team benchmarked Databricks Genie at 9.50% accuracy with an empty configuration, rising to 69.23% once column descriptions existed. Same product, same benchmark - the difference was metadata.

Now try the dashed trap lever, analytics reads direct from cloud storage. The bill jumps by $1,784 a month - $21,402 a year - on AWS's published egress tiers, for exactly the same work. b2 is entirely about why.

Say the sequencing rule out loud: self-serve is layer eight. Buying it first does not fail loudly. It fails quietly, by producing confident wrong answers that nobody flags.

Same product, same benchmark - only the metadata changed 0% 50% 100% accuracy empty configuration 9.50% with column descriptions 69.23% The difference was metadata, not a better model - and metadata is work only you can do. Databricks' own guidance: up to 30 tables or views, and "aim for five or fewer." Benchmarked by Microsoft's engineering team, with a published and reproducible method. Self-serve is layer eight. Bought first it fails quietly, in confident answers nobody flags.
🔍 Click to zoom - the missing layer shows up as a wrong answer, not an outage
Real world

Databricks' own best-practices page is the honest product spec. It states that "Quality table and column descriptions in Unity Catalog are critical for Genie accuracy," that "Genie Agents support up to 30 tables or views," and recommends you "Aim for five or fewer tables. The more focused your selection, the better." Five tables is a curated data mart. Set that against any vendor framing of "ask any question of all your data" - including from the same vendor. The tool is real and useful; the framing is not.

Homework

Try it yourself - this week ◐ 30 min total

Source material

Official sources covered

This track is built on vendors' own documentation and billing feeds, published engineering blogs from companies that built these platforms, and peer-reviewed work where it exists - with marketing claims labelled as such. Every price carries its fetch date. This page covers:

✓AWS S3, Cloudflare R2, Wasabi published rate cards (fetched 2026-08-06/07)The cost model behind both demos · full storage economics in b2
✓Airbnb engineering blog - Dataportal (2017), Minerva (2021), Metis (2023)The six-year platform arc · revisited per layer through the track
◐Microsoft ISE evaluation of Databricks Genie on LiveSQLBench (2026-05-07)Previewed in Demo 2 · the full evidence session is b9
◐Databricks, Snowflake, Microsoft Fabric platform documentationThe three unification axes · lakehouse detail in b2 and b5
◐NVIDIA AI Enterprise pricing page (updated 2026-06-08)The MLOps line in the bill · full compute economics in b7
Check yourself

Three questions before you go 🎯 ◐ 90 seconds

1 · You switch on storage and catalog. The bill reads $1,578 a month and zero personas are unblocked. What is the correct reading?

Nobody's job title is "uses the object store." Foundation layers pay off indirectly, through every layer above them - which makes them the hardest to justify in a budget review and the most expensive to retrofit later.

2 · With self-serve on and the semantic layer off, the business client is unblocked but flagged red. Why is that worse than being blocked?

Microsoft's evaluation measured this: 9.50% accuracy on an empty configuration versus 69.23% with column descriptions. The failure mode is not broken SQL, it is syntactically valid SQL carrying wrong business logic - which nothing catches.

3 · A vendor demos a model registry with approval workflows. What is the chokepoint test?

A chokepoint governs only if it is the only door. If the answer is "policy" rather than "architecture," it is a suggestion, not a control - and it will govern exactly the people who were already following the rules.

Practitioner session 1 cheat sheet · pin this

The eight layersStorage · table format + catalog · orchestration · engine · semantic + BI · compute + MLOps · LLM gateway · self-serve + governance.
The five personasDE needs layers 1-3 · DA needs 1-5 · DS needs 1-4 + 6 · AI engineer needs 1-2, 4, 7 · client needs 1-5 + 8.
The ladder$0 → $1,578 (0 unblocked) → $2,178 (DE) → $5,878 (DA) → $9,395 (DS) → $9,795 (AIE) → $11,295 all five. $135,540/year.
The sequencing ruleSelf-serve is layer eight. Buying it first fails quietly - confident wrong answers, not error messages.
The chokepoint frameEvery layer has a narrow waist where truth is decided: the catalog, the metric definitions, the registry, the gateway.
The chokepoint test"What stops someone going around this?" Architecture is a control; policy is a suggestion.
Registry = gatewaySame pattern, two eras: models you train, models you rent. Both answer what's running, whence, who approved, how to roll back.
The evidence to rememberGenie at 9.50% empty vs 69.23% with column descriptions. You buy metadata quality, not accuracy.