Performance Testing Service (PTS) applies load to your system in one of two modes: virtual user (VU) mode or requests per second (RPS) mode. Each mode controls a different dimension of load, and the right choice depends on what you need to measure.
| Mode | What it controls | Best for |
|---|---|---|
| VU mode | Number of concurrent users | Testing how many simultaneous users your system handles |
| RPS mode | Throughput (requests per second) | Testing the maximum request rate your system sustains |
Choose a load mode
Select the mode that matches your system's real-world traffic pattern:
VU mode -- Use when you want to answer: *"How does my system behave under N concurrent users?"* VU mode simulates a fixed pool of users, each running a business session end to end. This fits scenarios where you need to assess how many concurrent online users each node of a business system can handle.
RPS mode -- Use when you want to answer: *"Can my system sustain N requests per second?"* RPS mode drives a target throughput against each API in your scenario. This fits scenarios where you want to use RPS as a metric to measure the number of requests that a system can handle in a second.
VU mode
In VU mode, load equals the number of concurrent virtual users interacting with your system.
How VU mode works
Set the maximum number of virtual users for the entire scenario.
Assign a weight to each business session to distribute VUs proportionally.
PTS creates the specified number of VUs and distributes them across business sessions.
Because APIs within a session have different response times, VUs accumulate unevenly across APIs. A slow API holds more VUs at any given moment, consuming more thread resources.
Example: A scenario has 100 VUs running a business session with two APIs. If API 1 has a fast response speed and API 2 has a slow response speed, more virtual users wait at API 2, which requires more thread resources to handle virtual user requests.
VU mode parameters
After you select VU mode, configure the following parameters in the Load Level Configuration section:
| Parameter | Description |
|---|---|
| Weight of Max VU | Distributes total VUs across business sessions by weight. For example, if session A has weight 1 and session B has weight 3, session A receives 25% of total VUs and session B receives 75%. |
| Starting Percentage | The percentage of maximum VUs to begin with. Default: 10%. |
Example: A scenario allows 1,000 maximum VUs with two sessions (weights 1 and 3). Session A starts with 25 VUs (250 x 10%) and ramps up to 250. Session B starts with 75 VUs (750 x 10%) and ramps up to 750.
RPS mode
In RPS mode, load equals the number of requests per second sent to each API.
How RPS mode works
Set the Max RPS and Starting RPS for each API in your scenario. To match a throughput target, set RPS equal to the target transactions per second (TPS). For example, to verify that your system sustains 500 TPS, set RPS to 500.
PTS generates requests at the target rate, creating as many VUs as needed to sustain that rate.
Adjust the load manually during testing -- RPS mode does not auto-scale. For details, see Adjust the number of concurrent users.
If backend response times increase, PTS creates additional VUs to maintain the target RPS. This can cause a rapid, unexpected spike in VU count. Stop the test if you observe abnormal VU growth or system exceptions.
Funnel constraint
In a business session, each subsequent API must have an RPS value equal to or lower than the previous API. This reflects the natural drop-off in a user journey -- not every user who views a page goes on to complete a purchase.
Example (e-commerce funnel):
| Step | API | Max RPS |
|---|---|---|
| 1 | View homepage | 1,000 |
| 2 | View product details | 300 |
| 3 | Add to cart | 100 |
| 4 | Place order | 30 |
| 5 | Complete payment | 20 |
Each step has fewer requests than the one before it, matching real-world user behavior.
RPS mode parameters
| Parameter | Description |
|---|---|
| Max RPS | Maximum requests per second for an individual API. |
| Starting RPS | Initial requests per second for an API at the start of the test. |
Configure parameters in bulk
Both VU mode and RPS mode support bulk parameter configuration:
Select the business sessions (VU mode) or APIs (RPS mode) to configure.
Click Batch Settings in the upper-right corner.
Enter a value and click OK.
Resource plan limits
Regardless of the mode you select, the sum of maximum VUs or maximum RPS in each scenario cannot exceed the maximum VUs or RPS of your resource plan.