Application delivery is the combination of technologies and practices that ensure applications are served to end users quickly, securely, and reliably — regardless of scale, location, or infrastructure complexity. At its core, application delivery includes load balancing, traffic management, security, and acceleration working together to optimize every request between a client and a server.
Application delivery is essential to powering modern services that handle millions of concurrent requests — often stemming from millions of users — without impacting performance. It also helps teams approach that coveted 99.999% uptime goal, which ensures organizations maintain revenue, trust, and thus competitiveness with peers in their industry.
Plus, applications are no longer the monolithic monsters they once were. Apps, APIs, and AI services are now built with a decoupled microservices infrastructure, which emphasizes rapid feature development and easier maintainability. These services are now distributed across clouds, containers, and edge locations. This makes application delivery far more complex than in the past. Keeping track of everything is one challenge, but delivering apps to all corners of the globe can seem like an insurmountable task.
Successful application delivery means bridging the gap between where services run and where users are. Application delivery vendors aim to accomplish this while minimizing latency, increasing overall throughput (making their services more scalable), ensuring seamless communication between services, and upholding visibility across environments.
How does application delivery work?
While each vendor offers its own approach to application delivery, the following application delivery components are commonly shared between platforms.
Load balancing
Load balancing is the foundation of application delivery. It involves distributing incoming traffic across multiple backend servers — often based on preconfigured routing rules and load-balancing algorithms — to prevent performance loss and disruptions. This might be measurable using metrics we've mentioned earlier, such as latency, throughput (requests per second), bandwidth consumption, and others. Without load balancing, services would be much more prone to slowdowns and crashes.
Load balancing occurs at both Layer 4 (transport layer) and Layer 7 (application layer) of the Open Systems Interconnection (OSI) Model. Layer 4 load balancing is generally easier to implement, while Layer 7 is trickier due to complexities with protocol awareness and content-based routing. For example, users setting up Layer 7 load balancing may configure routing based on application data (URLs, cookies, and headers) or on a per-service basis.
Meanwhile, Layer 4 load balancing works based on TCP/UDP port(s) without needing to know application-level protocol information. It's typically less flexible than its Layer 7 counterpart, but comes with less added latency. That doesn't mean that Layer 7 load balancing isn't fast. However, it takes more effort and know-how to implement.
Application delivery controllers (ADCs)
ADCs are advanced load balancers that add essential app delivery functions such as SSL/TLS termination, mutual TLS (mTLS) support, HTTP compression, caching, and health checking. They may also incorporate other security features to help safeguard data.
Application delivery controllers work as reverse proxies that sit between clients and application servers. Like load balancers, they forward traffic to healthy servers, as you might expect. Their form factors have largely changed as technology and organizations have modernized. While starting as hardware appliances fit for on-premises deployments, ADCs are now mainly software-based. This change adds flexibility and cost efficiency.
It's also worth noting that hardware appliances need to be replaced over time. Their physical components must be upgraded to unlock better performance or new features — whereas software ADCs only require periodic updates tied to release cycles.
Application delivery networks (ADNs)
Application delivery networks work as globally distributed infrastructure components that help optimize delivery of dynamic application content. Behavioral triggers and other account-based actions enable experiences such as personalized shopping, resource access, and media viewing.
This distinguishes application delivery networks from content delivery networks (CDNs), which serve static user content. Conversely, these may include common images, text, and other virtual experiences that everyone can view. ADNs help optimize the complete application tech stack — including APIs.
ADNs combine load balancing, application acceleration (more later), and app security at the edge. They ensure that anyone anywhere can access content tailored for them, while keeping potential bad actors at arm's reach from your underlying infrastructure.
Global server load balancing (GSLB)
Both similar and supplemental to generic load balancing, global server load balancing directs clients to the nearest datacenter based on their geographical location. It also considers statuses such as server health and server load when determining the best routes for incoming traffic.
Global server load balancing (GSLB) is essential for multi-region and multi-cloud deployments spread across availability zones. This helps provide high availability and better performance. For example, you (as someone living in western Europe, let's say) wouldn't want your application to route you to an American datacenter when there are European equivalents healthy and waiting. That would add unnecessary latency to the request-response path and strain servers meant to handle other traffic. You instead gain overload protection, failover, and automatic health checking to keep your services running smoothly.
Application acceleration
One primary goal of application delivery is extracting full performance from your load balancing infrastructure. Application acceleration features such as HTTP compression, HTTP caching, connection pooling, multithreading, and even high-performance SSL/TLS libraries can make applications faster.
The goal is to reduce strain on backend servers, shrink the sizes of requests and responses, and take full advantage of underlying hardware to improve UX. This is true for consumer applications (YouTube, Netflix, etc.) and internal services that teams use regularly (Microsoft Active Directory, Tableau, etc.). By lowering latency and improving throughput, teams can create apps that are more responsive and resilient against traffic spikes.
Security features and services
Modern application delivery and security go hand in hand. Not only does strong security maintain availability, but the tradeoffs between security and performance aren't nearly as relevant anymore. Organizations now know they can protect their apps and traffic without adding excess latency or reducing RPS.
Organizations rely on features such as web application firewalls (WAFs), DDoS protection and rate limiting, bot management (for bots and botnets), and SSL/TLS processing to defeat attackers. Plus, organizations are turning more towards comprehensive application delivery and security platforms versus adopting multiple tools. Consolidation and centralization are reliable ways to reduce security complexity within your organization.
How has application delivery evolved?
Application delivery as a concept has existed for decades and has a rich history. Here's a brief timeline:
Early era (1990s–2000s) – Hardware load balancers handled basic traffic distribution. Application delivery was mainly a networking concern.
ADC era (2000s–2010s) – Hardware ADCs from vendors like F5 and Citrix added Layer 7 load balancing capabilities, SSL offloading, and basic compression. While offering iterative improvements, ADCs were largely expensive and inflexible. HAProxy also debuts and grows into the world's most widely used software load balancer.
Software-defined era (2010s–2020s) – Software load balancers such as HAProxy Enterprise and NGINX replaced hardware counterparts with greater flexibility, cost savings, and cloud compatibility. Kubernetes and microservices drove new delivery patterns.
Platform era (2020s–present) – Application delivery and security converge into unified platforms combining data planes, control planes, and edge networks. API gateways and AI gateways have since become crucial solutions as traffic has evolved.
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Does HAProxy support application delivery?
Yes! HAProxy One — the world's fastest application delivery and security platform — is built to handle application delivery for organizations of all sizes, HAProxy One seamlessly blends a high-performance data plane, a scalable control plane, and a global edge network to deliver the world's most demanding applications, APIs, and AI services in any environment.
Three main components comprise HAProxy One:
HAProxy Enterprise load balancer — A flexible data plane layer providing high-performance load balancing, an API/AI gateway, Kubernetes application routing, best-in-class SSL/TLS processing, and multi-layered security.
HAProxy Fusion Control Plane — A scalable control plane for full-lifecycle management, monitoring, and automation of multi-cluster, multi-cloud, and multi-team deployments.
HAProxy Edge — A globally distributed edge network that accelerates and secures application traffic worldwide.
Together, these components cover every layer of the application delivery stack, from load balancing and acceleration to WAF protection, bot management, and global traffic distribution.
If you want to see how HAProxy One performs in your own environment, request a demo and explore how it can streamline connectivity, strengthen security, and support high performance at scale.