Time to First Byte or TTFB – Another important Performance Quantity associated with Response Time is – Time To First Byte or TTFB in short. Time To First Byte is the Elapsed Time between submission of the request and receipt of the first response from the server. TTFB like Response Times can be measured either at the Application Tier level or within an Application Tier at any of system components i.e. CPU, Memory, Disk, Network, etc.

The Time To First Buffer is an indication of how heavy the processing for a given workload is or even an indication of how long does it take to open up a connection to a particular resource for the first time due to various buffering requirements. Time to First Buffer is used a lot by Performance Testing teams and is also used to optimize the way applications deliver their payload to customers. Time To First Buffer gains a lot of relevance with applications where the rendering times are significant.

Time To First Byte (TTFB)

Let’s take a look at an example to understand the relevance of Time To First Buffer.

Example: Let’s say the user has submitted an Order Submit request at time t=0s. Let’s assume that the overall response time for the transaction is 10s, but the client received the first response at t=5s while rest of the time is actually spent by the client GUI engine rendering the payload on the client machine while still receiving the rest of the payload from the server.

A large Time To First Buffer should be a cause of concern. From experience large TTFB could be due to any of the following reasons:

  • Lack of DNS caching
  • Lack of application caching
  • Challenges with the load balancing and networking setup causing delayed connections
  • Challenges with application performance delaying allocation of resources to initiate connections

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