- A
networks
Why wrong: networks defines network connections, not startup order.
- B
links
Why wrong: links is deprecated and does not control startup order.
- C
depends_on
depends_on with condition: service_healthy ensures the dependent service is healthy before starting.
Question 384 of 1,000
200-901 Application Deployment and Security Practice Question
This 200-901 practice question tests your understanding of application deployment and security. 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.
In a Docker Compose file, you want to ensure that the 'web' service starts only after the 'db' service is healthy. Which key should you use under the 'web' service?
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
✓
depends_on
In Docker Compose, the `depends_on` key with the `condition: service_healthy` option ensures that the `web` service starts only after the `db` service has passed its health check. This is defined in the `db` service using a `healthcheck` directive, and Compose waits for the healthy state before starting dependent services.
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.
- ✗
networks
Why it's wrong here
networks defines network connections, not startup order.
- ✗
links
Why it's wrong here
links is deprecated and does not control startup order.
- ✓
depends_on
Why this is correct
depends_on with condition: service_healthy ensures the dependent service is healthy before starting.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume `depends_on` alone (without `condition: service_healthy`) guarantees the dependent service is ready, but it only waits for the container to start, not for it to be healthy.
Detailed technical explanation
How to think about this question
Under the hood, Docker Compose uses the `depends_on` condition to poll the container's health status via the Docker Engine API, checking the `Health.Status` field. In real-world scenarios, this prevents race conditions where a web application attempts database connections before the DB is ready to accept queries, especially when the DB has initialization scripts or replication lag.
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 practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
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FAQ
Questions learners often ask
What does this 200-901 question test?
Application Deployment and Security — This question tests Application Deployment and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: depends_on — In Docker Compose, the `depends_on` key with the `condition: service_healthy` option ensures that the `web` service starts only after the `db` service has passed its health check. This is defined in the `db` service using a `healthcheck` directive, and Compose waits for the healthy state before starting dependent services.
What should I do if I get this 200-901 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 200-901 practice question is part of Courseiva's free Cisco 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 200-901 exam.
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