What does this AdTech Foundations page explain?

It explains how programmatic advertising works from ad request to conversion, including auctions, delivery, measurement, common failures, and practical metrics.

Who should use this guide?

It is designed for learners who already know the basic AdTech terms and want a stronger working model for day-to-day troubleshooting and interview preparation.

How should I study this page?

Start with the request flow, then review failures and metrics, and finish with examples and interview questions to turn definitions into practical recall.

Core Track

AdTech Foundations

This guide is for learners who want the full picture: request flow, auction logic, delivery, measurement, and the metrics discussed in AdTech interviews and day-to-day work.

Open the flow User Journey Interview Prep AdTech glossary

User Journey

How the user journey connects to the ad journey

AdTech becomes easier when you follow one person through the system. The user is not separate from the auction. Their screen, consent state, content context, and later actions shape the request, the win, and the final measurement story.

Audience arrives

A real person opens a publisher page or app. That creates the ad opportunity, but no revenue happens yet.

Context gets packaged

The site or app sends placement, device, consent, geo, and content context into the ad request so buyers know what they are evaluating.

Auction runs

The SSP or exchange fans the request out to eligible DSPs, which decide whether the impression matches targeting, budget, and quality rules.

Winning creative returns

The winning bid travels back with markup, media, trackers, and metadata. Any bad creative, timeout, or rejection can still stop delivery here.

Ad renders

The browser, app, or player renders the ad. Impression tracking, viewability, and click paths all depend on this layer working correctly.

User acts and systems measure it

If the user clicks or converts, the advertiser and measurement stack connect that action back to the winning impression for reporting and optimization.

Programmatic Advertising Flow

Interactive Diagram

Use the diagram and jump rail to follow the request path, response path, auction outcome, delivery, and measurement loop in one view.

Open App Ad Request Ad Server SSP Exchange DSPs DSP Rules No Bid Bid Response Response Auction Delivery Impression Click Conversion Optimize

The full request path

Step-by-step explanation

Sixteen steps from the first request to KPI review, written so you can understand what happens at each handoff in the chain.

User opens the site or app

A real user lands on a publisher page or app screen, which creates an ad slot that can now be sold.

Publisher creates the ad request

The page or app collects slot details, device context, location, time, identifiers, consent signals, and other fields needed to ask for an ad.

Site or app calls the ad server

The publisher property asks the ad server what demand source should handle this slot.

Ad server sends the opportunity to the SSP

If the impression is eligible for programmatic demand, the ad server forwards the request with placement rules, floor logic, and publisher priorities.

SSP forwards it to the ad exchange

The SSP packages the request with slot size, format, floor, site or app details, device data, IDs, geo, and consent information.

Ad exchange sends bid requests to DSPs

The exchange fans the same opportunity out to eligible buyers so multiple DSPs can evaluate it at once.

DSP checks advertiser rules

The DSP matches the request against targeting, budget, pacing, frequency, brand safety, predicted CTR, predicted CVR, and expected ROAS.

DSP may reject or no-bid

If the request does not fit targeting, quality rules, consent requirements, or budget controls, the DSP simply returns no bid.

DSP sends the bid response

If the impression is valuable, the DSP sends back a bid price, creative markup, adomain, trackers, and metadata needed for billing and validation.

Response path goes back through the chain

The response returns from DSP to exchange to SSP to ad server, and each hop can still reject it if the markup is invalid, late, or blocked.

Auction picks the winner

The ad server or exchange compares all valid bids and selects the winning bid based on price, deal priority, and publisher controls.

User sees the ad

The winning creative loads in the browser, app, or video player. If rendering succeeds, impression delivery is complete.

After delivery checks happen

Impression, viewability, and fraud checks start running once delivery conditions are met.

User clicks the ad

If the user engages, click tracking logs the click and sends the user to the landing page or app store.

User completes an action on the site

The advertiser site or app records actions such as signup, add to cart, purchase, install, or subscription through pixels, SDKs, or postbacks.

KPI review and optimization happen

The advertiser and DSP review CTR, CPA, ROAS, win rate, and quality signals so the next auction can perform better.

AdTech in one line: the publisher tries to sell an impression, advertisers try to buy the right user, and an auction decides which ad the user sees.

Debugging

Where things go wrong

A practical troubleshooting table for common delivery, auction, tracking, and CTV failures.

Step	Problem	Reason	Fix
SSP	Low bid requests	Floor price high	Reduce floor
DSP	No bid	Targeting mismatch	Expand targeting
DSP	No bid	Budget finished	Increase budget
Exchange	Lost auction	Bid too low	Increase bid
Creative	VAST error	Wrong format	Upload correct VAST
Impression	Not counted	Tracker missing	Fix tracker
Click	Click not tracked	Click tracker missing	Add click tracker
Conversion	Not tracked	MMP not integrated	Fix postback
Delivery	Under-delivery	Geo/device mismatch	Expand targeting
CTV	SSAI timeout	Ad too long	Fix ad duration

Measurement

Metrics at each step

This is the bridge between technical flow and business performance.

Step	Metric	Formula
Request	QPS	Requests per second
DSP	Bid Rate	Bids / Requests
Auction	Win Rate	Wins / Bids
Delivery	Fill Rate	Impressions / Requests
Click	CTR	Clicks / Impressions
Conversion	CVR	Conversions / Clicks
Revenue	eCPM	Revenue / Impressions * 1000
Performance	CPA	Spend / Conversions
Performance	ROAS	Revenue / Spend

Simple campaign math example: $1,000 budget at $2 CPM
Impressions	500,000 ($1,000 / $2 CPM × 1,000)
Clicks	10,000 (2% CTR)
Conversions	500 (5% conversion rate)
Revenue	$2,500
ROI	150%

Real payloads

Real OpenRTB, VAST, and tracker examples

Technical samples you can read line by line while learning how programmatic delivery really works.

OpenRTB Bid Request Example

A simplified bid request showing video inventory, device context, app name, and floor.

JSON

{
  "imp": [
    {
      "id": "1",
      "video": {
        "mimes": ["video/mp4"],
        "minduration": 15,
        "maxduration": 30
      },
      "bidfloor": 5.0
    }
  ],
  "device": {
    "ua": "CTV",
    "geo": {
      "country": "IND"
    }
  },
  "app": {
    "name": "Samsung TV Plus"
  }
}

Bid Response Example

The DSP returns price, creative markup, and creative ID if it wants the impression.