Performance Evaluation of API Gateways in Microservices System: No Gateway, Kong, and Native
API Gateway selection is a critical architectural decision in microservices systems, yet empirical comparisons between competing gateway strategies are scarce, particularly for PHP-based systems at the SME scale. This study presents a comparative performance analysis of three API Gateway implementations within System XYZ, a veterinary clinic management microservices architecture: No Gateway (direct client-to-service), Kong Gateway (third-party), and Native (Laravel). Performance testing was conducted using Apache Bench across three endpoints and three workload levels with three runs each. All 81 runs recorded zero failed requests. No Gateway consistently achieved the highest throughput (up to 6.68 req $/ \mathrm{s})$ and the lowest mean response time across all scenarios. Kong Gateway introduced minimal overhead on complex queries (0.6-8.3%) but exhibited severe latency spikes due to connection pool exhaustion and required significantly more memory (1.0-1.4 GB) than No Gateway (142-173 MB) and Native (149-238 MB) when backed by a single-threaded PHP server. Native incurs approximately three times higher response time for simple and filtered queries, and approximately two times higher for complex queries, due to the double PHP-hop overhead. These findings may inform developers of small-scale Laravel microservice systems in selecting the appropriate API Gateway strategy.