- A
Brute-force index (exact neighbor search)
Why wrong: Brute-force does not support streaming updates and is slow for large datasets.
- B
ANN index with the 'streaming' update mode
Streaming mode allows incremental updates without full index rebuild.
- C
ANN index with the 'batch' update mode
Why wrong: Batch mode requires full rebuild, not suitable for frequent updates.
- D
Tree-AH index
Why wrong: Tree-AH is an algorithm, not a deployment mode; it may not support streaming.
Question 815 of 1,000
PMLE Serving and Scaling Models Practice Question
This PMLE practice question tests your understanding of serving and scaling models. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are using Vertex AI Vector Search to find nearest neighbors for a recommendation system. Your index is built on 10M embeddings and you need low-latency queries. You want to ensure that adding new embeddings does not require a full index rebuild. Which index type should you use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ANN index with the 'streaming' update mode
The ANN index with 'streaming' update mode is correct because it supports real-time insertion of new embeddings without requiring a full index rebuild, which is essential for low-latency recommendation systems. This mode uses a separate unsearched buffer for new vectors and periodically merges them into the main index, enabling continuous updates while maintaining query performance.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Brute-force index (exact neighbor search)
Why it's wrong here
Brute-force does not support streaming updates and is slow for large datasets.
- ✓
ANN index with the 'streaming' update mode
Why this is correct
Streaming mode allows incremental updates without full index rebuild.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
ANN index with the 'batch' update mode
Why it's wrong here
Batch mode requires full rebuild, not suitable for frequent updates.
- ✗
Tree-AH index
Why it's wrong here
Tree-AH is an algorithm, not a deployment mode; it may not support streaming.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that all ANN indexes support incremental updates, but only the 'streaming' mode in Vertex AI Vector Search avoids full rebuilds, while 'batch' mode and Tree-AH require periodic full reindexing.
Detailed technical explanation
How to think about this question
Under the hood, the streaming update mode in Vertex AI Vector Search leverages a two-tier architecture: a main ANN index (e.g., ScaNN) for serving queries and a separate 'unsearched' buffer for newly inserted embeddings. Queries first search the main index, then merge results with a brute-force scan of the buffer, and the buffer is periodically merged into the main index via background jobs. In real-world scenarios, this allows a recommendation system to ingest user behavior embeddings within seconds of generation, avoiding stale recommendations while keeping p99 latency under 10ms.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Serving and Scaling Models — study guide chapter
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FAQ
Questions learners often ask
What does this PMLE question test?
Serving and Scaling Models — This question tests Serving and Scaling Models — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ANN index with the 'streaming' update mode — The ANN index with 'streaming' update mode is correct because it supports real-time insertion of new embeddings without requiring a full index rebuild, which is essential for low-latency recommendation systems. This mode uses a separate unsearched buffer for new vectors and periodically merges them into the main index, enabling continuous updates while maintaining query performance.
What should I do if I get this PMLE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This PMLE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PMLE exam.
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