The role of proxies in ensuring the correct operation of API requests

Modern APIs impose high requirements on availability, speed, and response predictability. Modern proxies occupy key positions in API infrastructure by providing traffic control, secure access, and service resilience. Therefore, a properly designed proxy infrastructure makes it possible to control request routing, balance load, and accelerate data processing without compromising service quality.

What an API is and why request stability matters

An API is a set of rules and interfaces through which programs interact with each other. It defines request and response formats, authorization mechanisms, error handling, and versioning principles.

Why request stability matters

• User experience. Delays and errors directly affect satisfaction and trust in the product.
• Business reliability. Clients and partners evaluate a service by its availability and response speed.
• Analytics and planning. Predictable response parameters allow metrics to be measured correctly, forecasts to be built, and processes to be optimized.
• Development and testing. Stability simplifies the rollout of new features and speeds up troubleshooting without constant struggle with unpredictability.
• Compatibility and SLA. Many services require specific availability and response time levels; stable requests help meet promised indicators.

How a proxy works in API interaction

What an API proxy does

An API proxy acts as an intermediary between the client and the backend service. The client sends a request to the proxy without knowing where the target service is actually located. The proxy accepts the request, applies security and routing policies, and then forwards it to the required backend API. The response returns through the proxy and, if necessary, is transformed into a client-friendly format. This way, the client gains access to the API without knowing infrastructure details.

How a proxy processes incoming and outgoing requests

1. The client sends a request to the proxy

The request contains the endpoint address, headers (including Host and others required), the HTTP method, and the body or query parameters.

2. The proxy ensures security and validity

Checks and security measures are performed: authentication, authorization, speed control, filtering, abuse protection, sometimes TLS termination and logging.

3. The proxy forwards the request to the backend

The proxy selects a suitable backend, establishes a connection, and sends the request. If necessary, it can adjust the path, headers, or parameters and add tracing data.

4. The backend processes the request and responds to the proxy

The backend receives the request, processes it, and returns the response over the same connection to the proxy.

5. The proxy processes the response before the client receives it

The proxy can transform the response to the format required by the client, normalize headers, apply caching or compression, or hide internal architecture details.

6. The proxy sends the response to the client

The final response is delivered to the client, which then processes the data as usual.

Main proxy tasks when working with APIs

Request route optimization

• The proxy selects the most efficient path to the backend API, taking into account latency, load, and geographic location. This reduces latency and increases response speed.
• Load and node health information is used to route traffic through the least loaded or closest entry points.

Load balancing under high request volume

• The proxy distributes incoming requests so that no node becomes overloaded.
• Balancing methods are applied: round-robin, least active connections, response-time-based, and others. Node availability checks are performed regularly.

Response caching to accelerate repeated requests

• Frequent or repetitive data is cached at the proxy layer, reducing access time and backend load.
• Cache lifetime (TTL), event-based refresh, and invalidation mechanisms are managed to keep data up to date.

Traffic control and statistics collection

• The proxy limits request rates (rate limiting), sets priorities, and ensures quality of service for different clients or services.
• Metrics collection and aggregation: latency, throughput, error rate, logs, and traces. This data helps quickly detect problems and plan resources.

Improving request reliability and stability

A proxy is not just a router but an intelligent gateway between clients and backend services. It continuously monitors availability and performance of nodes, applies resilience policies, and manages traffic so that connection errors occur less often. When one backend becomes unavailable, the proxy automatically redirects requests to other working replicas, significantly reducing the risk of failures and delays. If a problem is temporary, the proxy initiates retries with controlled delays, ensuring effective operation even during short-term faults. In extreme cases, a built-in circuit breaker mechanism can temporarily disable calls to a problematic node to avoid overload and prevent cascading system failure.

In addition, the proxy can adaptively route traffic in real time, taking into account current latency and server status to keep response times low and prevent overload of individual components. As a result, client interaction with the service becomes more stable, and the probability of failures decreases due to a comprehensive approach to monitoring, load management, and automatic recovery actions.

Security and data control

A proxy can significantly improve security of data exchange between clients and services through several key mechanisms.

• First, encryption.

A secure TLS connection is usually established between the client and the proxy, ensuring confidentiality of transmitted information in transit. Depending on the architecture, different modes can be used: TLS termination at the proxy (when the proxy decrypts traffic and forwards it further to the backend in encrypted form) or TLS pass-through (preserving end-to-end encryption to the backend). In some scenarios, mutual TLS authentication (mTLS) is applied, where the client, proxy, and backend authenticate each other using certificates.

• Second, data leak protection.

The proxy can reduce leakage risks through filtering and data processing at the boundary: log minimization, masking or tokenization of sensitive fields, application of least-privilege data access policies, and DLP measures. During logging, only the necessary metadata can be stored to avoid collecting PII or commercially sensitive information. Additionally, the proxy provides access control and auditing.

Practical usage examples

Using a proxy in high-load systems

During peak loads in large systems, the proxy acts as an API access control center and a traffic optimization point. It routes to the most available backend nodes, applies rate limiting and intelligent balancing, caches frequent responses, and collects performance metrics. This reduces latency, maintains high availability, and evenly distributes load across regions and services.

Use in API testing

In a test environment, a proxy helps conduct effective API testing. It can emulate network delays and errors, inject artificial latency or faults, intercept and modify requests and responses, reproduce predictable scenarios, and verify client and API contract behavior without affecting production. The proxy also simplifies creation of test datasets by masking or substituting test values so that real customer information is not used.

Support for geo-distributed services

For geo-distributed services, the proxy serves as an edge-level entry point. Multiple proxy nodes are deployed in different regions, allowing requests to be routed to the nearest point of presence, reducing latency and enabling content localization. This approach simplifies compliance with data localization requirements, speeds up user responses, and increases resilience to regional failures. If necessary, the proxy can dynamically change routes depending on network conditions, backend status, and regional policies.

Choosing a proxy for APIs

When it comes to choosing a proxy, it is important to pay attention to key characteristics. A proxy should provide:

• minimal latency and high throughput;
• high availability and automatic failover between working nodes;
• content localization;
• TLS, mTLS capability, access control;
• rate limits, queues, priorities, overload protection;
• storage of frequently requested data for acceleration;
• clear pricing and support terms.

The proxy service Belurk is optimal for various tasks and suitable for different conditions thanks to the following characteristics:

• A global node network and intelligent traffic distribution ensure fast responses and the ability to process many requests.
• Real-time health monitoring.
• The ability to work through regional points of presence, which reduces latency and improves response relevance.
• Secure connections and flexible access rules to keep your data safe.
• Configuration of limits and queues to maintain stability even under sharp peak loads.
• Caching and local storage of popular responses for fast repeated access.

Belurk is a convenient choice for a wide range of tasks: from everyday operations and testing to large integrations and analytics. And all this without the need to dive into complex technical details.