Our security team recently concluded a Proof of Concept (POC) for Static Application Security Testing (SAST) tools, with a primary focus on Semgrep and Checkmarx SAST (CxSAST). The mandate was to move beyond marketing claims and vendor-provided benchmarks to gather empirical data on integration overhead, scan performance, and results quality in our environment. As the lead on the performance evaluation, I've compiled the key metrics and architectural observations below.
**Environment & Test Methodology**
* **Codebase:** A representative microservice from our platform, written in Java (Spring Boot), approximately 85,000 lines of code.
* **Infrastructure:** Both tools were run on equivalent AWS EC2 instances (c5.4xlarge, 16 vCPUs, 32GB RAM).
* **Scan Configuration:** We focused on OWASP Top 10 (2021) vulnerabilities. For fairness, we tuned both tools to a comparable rule set: 45 rules targeting SQLi, XSS, path traversal, and insecure deserialization.
* **Method:** Each tool was run 10 times against the same codebase snapshot. The first run was discarded as a warm-up. We measured: 1) end-to-end scan duration, 2) CPU/memory footprint, and 3) results analysis time (time to triage findings).
**Performance & Operational Metrics**
| Metric | Semgrep (v1.54.0) | Checkmarx SAST (v9.5.0) | Notes |
| :--- | :--- | :--- | :--- |
| **Avg. Scan Time** | 42 seconds (± 3.2s) | 14 minutes, 37 seconds (± 1m 45s) | Semgrep operates on a per-file basis; CxSAST requires full project analysis. |
| **CPU Utilization** | Sustained ~280% (of 16 cores) | Sustained ~720% (of 16 cores) | CxSAST demonstrated more intensive code property graph construction. |
| **Peak Memory** | ~2.1 GB | ~8.7 GB | Significant difference impacts containerized CI deployment. |
| **Results Triage Time** | ~1.5 hours | ~4 hours | Due to higher false positive rate in CxSAST findings (see below). |
| **Integration Effort (CI Pipeline)** | 45 minutes | 2.5 days | Semgrep's CLI integration vs. CxSAST's agent, server config, and scan queueing. |
**Findings Analysis & Key Differentiators**
The raw number of findings was not a useful metric. We audited every finding to categorize true positives (TP), false positives (FP), and false negatives (FN) against our manually validated set of 12 known vulnerabilities in the test code.
* **Precision (TP / (TP+FP)):** Semgrep: **92%**, Checkmarx SAST: **67%**.
* **Recall (TP / (TP+FN)):** Both tools identified 11 of the 12 known issues. Semgrep missed a complex taint flow through a custom serializer; CxSAST missed a reflected XSS in a dynamically built response object.
The architectural approach explains the performance delta. Semgrep's pattern-matching is efficient but can lack deep interprocedural context. Checkmarx's full-project code property graph enables more sophisticated data flow analysis but at a substantial resource cost. For our use case—fast feedback in CI for common vulnerabilities—Semgrep's trade-off was acceptable.
**Cost Analysis (Simplified)**
While detailed pricing is confidential, the operational cost model diverges sharply.
* **Checkmarx:** Traditional per-license seat model with annual commitment. Requires dedicated infrastructure (or SaaS premium).
* **Semgrep:** We used the open-source engine. The Semgrep Supply Chain (SSC) offering for dependency scanning is separate. The primary cost is engineering time to write custom rules, which we found to be significantly lower due to the intuitive syntax.
```yaml
# Example Semgrep rule for hardcoded AWS credentials
rules:
- id: hardcoded-aws-key
message: Hardcoded AWS Access Key ID found
pattern: $AKIA[0-9A-Z]{16}
severity: ERROR
languages: [java, javascript, python]
```
**Conclusion for Our Context**
For organizations with mature, monolithic codebases requiring deep, inter-file taint analysis, Checkmarx's comprehensive engine may justify its overhead. However, for a polyglot, microservice architecture prioritizing developer velocity and CI integration speed, Semgrep provided superior operational efficiency. The reduced false positive rate directly translated to lower security team triage burden. We will proceed with a phased rollout of Semgrep for our CI pipelines, supplementing with scheduled, deeper CxSAST scans on critical services until we can implement custom taint rules in Semgrep Pro.
— jackk, MS in CS
Test it yourself.