300-445 Question 198
Single answerA web application hosted on your enterprise network is experiencing slow load times. Using browser waterfall data, you identify that the majority of the delay occurs during the 'waiting (TTFB)' phase. What is the most likely cause of this issue?
- A
High server-side processing time on the web server.
- B
Large image files being downloaded by the browser.
- C
A high number of third-party scripts being loaded.
- D
Slow DNS resolution for the application domain.
Show answer and explanation
Correct answer: A
Explanation
The 'waiting (TTFB)' phase in a browser waterfall chart represents the time taken by the server to respond after receiving a request. A prolonged TTFB is typically caused by issues on the server side, such as high processing times due to complex logic, database latency, or overloaded server resources. Diagnosing this issue helps narrow down the root cause of the performance bottleneck.
- A. Correct.
High server-side processing time directly impacts the Time to First Byte (TTFB), as the server takes longer to generate the response after receiving the request.
- B. Incorrect.
Large image files would impact the 'download' phase in the browser waterfall, not the 'waiting (TTFB)' phase.
- C. Incorrect.
A high number of third-party scripts would contribute to increased load times but primarily impact subsequent phases such as script execution or rendering, not the TTFB.
- D. Incorrect.
Slow DNS resolution would cause delays in the 'DNS Lookup' phase, not the 'waiting (TTFB)' phase.