Many webmasters and enterprise operations personnel often come across two common terms: QPS protection and DDoS protection. Because both are related to defending against high concurrent traffic and malicious attacks, many people often confuse them, even considering them the same concept. However, there are significant differences between the two in terms of definition, application scenarios, response methods, and protection objectives.

　　QPS stands for queries per second and is commonly used to measure the concurrent access capacity of a website, interface, or system. For an e-commerce website, user clicks, searches, and orders all generate requests, ultimately reflecting changes in QPS. If traffic surges at a given point in time, exceeding the system's capacity, service responses can be slow or even crash. Therefore, the core of QPS protection is to limit and optimize the number of requests that can be processed per second, ensuring stable service operation during normal business peaks or sudden traffic bursts. This protection approach is more about "rate limiting, traffic diversion, caching, and code and database optimization." It is a means of preventing overload and ensuring performance, rather than a purely security measure to counter malicious attacks.

　　A DDoS attack, or distributed denial of service attack, is a malicious exploitation of network resources. Attackers control a large number of zombie machines or botnets to flood the target server or network device with requests or data packets, aiming to exhaust server resources and network bandwidth, rendering legitimate users unable to access the service. DDoS attacks are not normal business traffic, but rather an asymmetric war of attrition. Attackers can mobilize thousands of nodes with minimal resources, while defenders must consume vast amounts of bandwidth, hardware, and protective equipment. DDoS protection focuses on identifying malicious traffic without impacting legitimate users, and then scrubbing, discarding, or redirecting it to ensure business continuity.

　　From this perspective, the difference between QPS protection and DDoS protection becomes clear. The former targets high-concurrency requests at the business level, primarily aiming to optimize performance and resource utilization, enabling the system to withstand higher concurrency. The latter targets external attacks, focusing on security protection to mitigate the risk of system downtime caused by malicious traffic. In other words, QPS protection is more like physical training, improving server fitness and enabling it to run longer; whereas DDoS protection is more like defensive armor, protecting against the fiercest attacks launched by the enemy. While the two are not fundamentally the same concept, they do overlap and complement each other in certain situations.

　　For example, in high-concurrency scenarios, the system needs to protect against QPS through methods such as rate limiting, load balancing, and CDN acceleration. If these mechanisms are robust, they can also, to a certain extent, resist small-scale DDoS attacks. This is because DDoS is essentially a high-volume impact, just malicious traffic. When your QPS protection mechanism can automatically discard abnormal requests and allocate resources appropriately, some of the attack traffic will be naturally mitigated. However, when facing large-scale, distributed DDoS attacks, relying solely on QPS protection is far from sufficient. A truly effective defense requires the support of professional scrubbing centers, anti-DDoS equipment, and high-bandwidth resources.

　　More specifically, QPS protection emphasizes application-level capacity, such as rate limiting at the Nginx, Redis, and database layers, or setting a maximum concurrency limit at the gateway layer to prevent abuse of a single interface. DDoS protection, on the other hand, involves the lower-level network and transport layers, encompassing various attack methods such as TCP SYN Flood, UDP Flood, and ICMP Flood. Protection measures include not only ACL filtering and firewall policies, but also technologies such as high-defense IP, BGP scrubbing, and traffic diversion. The two focus on different aspects: one is "stabilizing service performance," while the other is "ensuring service disruption."

　　Many enterprises employ both types of protection strategies when deploying their network security systems. For example, during the Double 11 shopping festival, a large e-commerce platform must first ensure QPS protection to ensure that the massive influx of real user requests does not overwhelm the server. Simultaneously, DDoS protection must also be enabled to prevent malicious traffic attacks from black and gray industries. This combination of two strategies ensures that the system can handle both normal business peaks and withstand abnormal traffic shocks.