Learn how to create, test, and compare the back-end HTTP services in Scala.

Become a Scala Developer

In this module, we will explore the functional aspects of Scala. We will start by looking at a small use case. We will then learn the difference between pure and impure implementations by looking into referential transparency and how functional programming relies on it. We will then gradually implement the use case in both pure and impure ways. Moving ahead, we will simultaneously build, test, and document the implementations and point out the tools required along the way. By the end of this module, we will have a substantial understanding of how these techniques work, their pros and cons, and how pure implementation can be more robust.

Pure Functional HTTP APIs in Scala

## Metrics Recap
To reiterate, we will be using the following metrics to benchmark our endpoints.
- **AVG**: The average response time in milliseconds
- **MED**: The median response time in milliseconds
- **90%**: 90 percent of all requests were handled within the response time in milliseconds or less. 
- **95%**: 95 percent of all requests were handled within the response time in milliseconds or less. 
- **99%**: 99 percent of all requests were handled within the response time in milliseconds or less. 
- **MIN**: The minimum response time in milliseconds
- **MAX**: The maximum response time in milliseconds
- **ERR**: The error rate in percent
- **R/S**: The number of requests per second that could be handled 
- **MEM**: The maximum amount of memory used by the service during the benchmark in MB
- **LD**: The average system load on the service machine during the benchmark
## Update 100.000 products
| **Metric** | **Impure** | **Pure**|
| --- | ---| --- |
| AVG (ms) | 78 | 12 |
| MED (ms) | 75 | 11 |
| 90 (%)| 104 | 16 |
| 95 (%) | 115 | 20 |
| 99 (%) | 140 | 34 |
| MIN (ms) | 42 | 5 |
| MAX (ms) | 798 | 707 |
| ERR (%) | 0% | 0% |
| R/S (sec) | 125.66 | 765.26 |
| MEM (MB) | 1176 | 1279 |
| LD | 16 | 8 |

Updating existing products results in nearly the same picture as the “create products” benchmark. Interestingly, the impure service performs about 20% better on an update than on a create. 

The other metrics are nearly identical to the first benchmark. The pure service uses a bit more memory (around 8%) but is around 6 times faster than the impure one, causing only half of the system load.

# Metrics Recap
To reiterate, we will be using the following metrics to benchmark our endpoints.
- **AVG**: The average response time in milliseconds
- **MED**: The median response time in milliseconds
- **90%**: 90 percent of all requests were handled within the response time in milliseconds or less. 
- **95%**: 95 percent of all requests were handled within the response time in milliseconds or less. 
- **99%**: 99 percent of all requests were handled within the response time in milliseconds or less. 
- **MIN**: The minimum response time in milliseconds
- **MAX**: The maximum response time in milliseconds
- **ERR**: The error rate in percent
- **R/S**: The number of requests per second that could be handled 
- **MEM**: The maximum amount of memory used by the service during the benchmark in MB
- **LD**: The average system load on the service machine during the benchmark
# Update 100.000 products
| **Metric** | **Impure** | **Pure**|
| --- | ---| --- |
| AVG (ms) | 78 | 12 |
| MED (ms) | 75 | 11 |
| 90 (%)| 104 | 16 |
| 95 (%) | 115 | 20 |
| 99 (%) | 140 | 34 |
| MIN (ms) | 42 | 5 |
| MAX (ms) | 798 | 707 |
| ERR (%) | 0% | 0% |
| R/S (sec) | 125.66 | 765.26 |
| MEM (MB) | 1176 | 1279 |
| LD | 16 | 8 |

Updating existing products results in nearly the same picture as the “create products” benchmark. Interestingly, the impure service performs about 20% better on an update than on a create. 

The other metrics are nearly identical to the first benchmark. The pure service uses a bit more memory (around 8%) but is around 6 times faster than the impure one, causing only half of the system load.

Learn how to add benchmarks for comparing pure and impure implementations.

Introduction

Impure Implementation

Pure Implementation

Testing Impure Services

Testing Pure Services

Benchmarks

Documentation

Conclusion

Adding Benchmarks - Part II

Metrics Recap