CDN Cost Optimization & Traffic Management 4 — Questions and Answers
Question 1: A CDN customer commits to 100 TB/month of data transfer under a reserved-capacity contract but only uses 60 TB. What is the likely financial outcome?
- They pay only for the 60 TB actually used
- They pay for the full 100 TB committed regardless of usage (Correct answer)
- They receive a credit for unused capacity on the next billing cycle
- The CDN automatically downgrades them to a smaller tier
Correct answer: They pay for the full 100 TB committed regardless of usage
Reserved-capacity contracts typically require payment for the committed amount whether or not the full volume is consumed.
Question 2: What is 'CDN request collapsing' and how does it reduce costs?
- Merging multiple CDN providers into one account
- Combining several customer accounts into a single bill
- Queuing duplicate simultaneous cache-miss requests so only one goes to origin (Correct answer)
- Batching log files to reduce storage costs
Correct answer: Queuing duplicate simultaneous cache-miss requests so only one goes to origin
Request collapsing (also called request coalescing) holds duplicate in-flight cache-miss requests and serves them all with a single origin response, reducing origin load.
Question 3: A CDN administrator wants to minimize log storage costs. Which approach is most cost-effective without losing critical visibility?
- Store all raw logs indefinitely at full granularity
- Use log sampling and aggregate metrics with alerting on anomalies (Correct answer)
- Disable all logging to eliminate storage costs
- Store logs on origin servers only
Correct answer: Use log sampling and aggregate metrics with alerting on anomalies
Log sampling reduces storage volume while aggregate metrics and anomaly alerts preserve operational visibility at a fraction of the full-log storage cost.
Question 4: Which CDN cost lever has the most direct impact on reducing 'cache fill' costs from origin to edge nodes?
- Increasing the number of PoPs
- Using origin shield (mid-tier caching) to consolidate origin requests (Correct answer)
- Enabling WebSockets at the edge
- Increasing DNS TTL
Correct answer: Using origin shield (mid-tier caching) to consolidate origin requests
An origin shield acts as a central cache tier that absorbs redundant requests from multiple PoPs, dramatically reducing the number of fills that reach the origin.
Question 5: A video platform uses adaptive bitrate (ABR) streaming. How does CDN configuration of ABR manifest files affect cost optimization?
- ABR manifests should never be cached as they change per-user
- Caching ABR manifests with short TTLs reduces origin polling while keeping streams current (Correct answer)
- ABR manifests should be served only from origin to ensure accuracy
- Caching ABR manifests has no effect on CDN costs
Correct answer: Caching ABR manifests with short TTLs reduces origin polling while keeping streams current
Short-TTL caching of ABR manifests balances manifest freshness for live streams with reduced origin request volume, lowering both latency and costs.
Question 6: What CDN concept describes the percentage of requests served from cache without hitting the origin?
- Origin offload rate (cache hit ratio) (Correct answer)
- Bandwidth utilization rate
- Edge-to-origin ratio
- Request success rate
Correct answer: Origin offload rate (cache hit ratio)
The cache hit ratio (origin offload rate) measures what fraction of total requests are served from edge cache; a higher ratio means lower origin costs.
Question 7: A company's CDN costs spike every weekend due to user-generated video uploads triggering transcoding and delivery. Which strategy best controls these costs?
- Block all uploads on weekends
- Use scheduled off-peak transcoding jobs and set upload size limits (Correct answer)
- Disable the CDN on weekends
- Switch to a flat-rate plan regardless of traffic
Correct answer: Use scheduled off-peak transcoding jobs and set upload size limits
Scheduling transcoding during off-peak hours and enforcing upload size limits reduces simultaneous compute and delivery costs during high-demand periods.
CDN Cost Optimization & Traffic Management 4
A CDN customer commits to 100 TB/month of data transfer under a reserved-capacity contract but only uses 60 TB.
What is the likely financial outcome?