Using the ABRA Flexi REST API opens up wide possibilities for integrating the system with other applications and automating common processes. However, for the integration to work reliably and efficiently, you need to follow certain rules and best practices. The right approach saves developers time, reduces system load, and prevents unnecessary errors when working with data.

In this article, we'll focus on recommended best practices to help you make the most of the API – from optimizing queries, proper pagination, and retry strategies, to working with error codes and understanding them. You'll also learn how to avoid duplicates, how to work with limits, and why it's important to think about security and data consistency already when designing your integration.

Authentication is a fundamental element of security when working with the REST API. If it's not set up correctly, sensitive data may be leaked or unauthorized access to the system may occur. That's why you need to use secure login and data transfer methods and avoid outdated or risky practices that could compromise the security of the entire integration.

Access credentials (usernames, passwords, API tokens) are the key to your data. If they fall into the wrong hands, a serious security incident can occur. That's why you must handle them with the utmost care and follow best practices that minimize the risk of a leak.

The goal isn't to "download everything," but to quickly get exactly what you need, with minimal load on both the network and the server. Think about how you use the data: what will you actually display, how often does it change, do you need to load it right away, or can part of it be pre-calculated or cached. Well-designed queries and data flow reduce response times, save API limits, and increase the stability of the entire integration.

You don't need to download all data again – it's more efficient to retrieve only the changes. This is what change feeds (Changes API) and push notifications (webhooks) are for. The Changes API is ideal for reliable client-driven delta synchronization (polling + cursor), while webhooks are ideal for a quick reaction to events without unnecessary polling. In practice, it's often best to combine both approaches.

Instead of downloading the entire agenda with every synchronization, it's better to only retrieve what has actually changed. Delta export significantly reduces data transfer, lowers the load on the API and database, and speeds up integration – especially for larger agendas or regular reporting.

When working with the REST API, don't run multiple identical queries at the same time. If you overdo it, the system becomes overloaded, and the result is usually slower performance or error responses. In cases of excessive overload, we may block access as a last resort, and unblocking it may need to be resolved with our support team.

That's why it's a good idea to handle parallel queries carefully and spread out calls smartly over time.

When communicating with the API, you may encounter a situation where the server rejects further requests because it's currently overloaded. This typically manifests as error code 429 – Too Many Requests.

In such a situation, it's not a good idea to immediately retry the request, as this would increase the load even further. The correct practice is to use so-called exponential backoff – gradually increasing the wait time between further attempts.

Respect the daily limit on the number of requests. The default limit may vary for your license depending on the purchased volume.

Correctly interpreting HTTP error codes is key to a reliable integration. Each code has its own meaning and helps distinguish whether the problem lies on the client side (a bad request, invalid data, missing permissions) or on the server side (temporary unavailability, internal error). This allows the application to respond correctly – either by fixing the data and resending the request, or by waiting and trying the action again later.

When writing to the API, it's important to ensure that a repeated request isn't processed multiple times and doesn't create duplicates. This typically happens when there's a connection failure or when using a retry strategy – the client isn't sure whether the request went through and sends it again. Without idempotence, this could result in multiple invoices, orders, or other documents being created, which is particularly problematic in accounting.

When integrating with the REST API, it's very useful to keep records of sent requests and received responses. Logs allow you to quickly find out why something isn't working, what the API actually returned, or what request was sent to the server. Logging is also an invaluable tool when communicating with customer support – instead of a vague description like "something went wrong," you have specific data available.

The API evolves over time – new fields are added, and sometimes the response format or logic changes. If your application isn't prepared for this, it may stop working when a change occurs. That's why it's important to write integrations that are resilient to changes while also keeping track of API developments.

A quality integration isn't just about calling the API correctly, but also about how easily it can be deployed, tested, and maintained. Separating test and production environments reduces the risk of errors, as does the right approach to data backups – these are better handled through the web interface than through the API.

Without ongoing visibility into how much and how often you're calling the API, problems are discovered too late. Basic monitoring helps you keep an eye on limits, tune performance, and prevent integration outages.

Following best practices when working with the ABRA Flexi REST API will help you build stable, secure, and sustainable integrations in the long run. Whether it's optimizing queries, handling error states, or securely managing access credentials, it always pays off to invest in the right design from the very beginning.

If you're not sure how to use the API in your specific scenario, or if you need more detailed recommendations, you can schedule an individual consultation, where we'll be happy to help you with the implementation.