API and System Integrations

What do API and system integrations solve?

API and system integrations let the software used in your business exchange data with each other without a person in between. A setup where an order placed on the website is typed into the accounting program by hand, tracking numbers are sent to customers one by one, or stock information is updated in Excel in the evenings both wastes time and produces errors.

The goal of an API integration is to make this carrying of data automatic, traceable and consistent. A piece of data is entered once and reaches all related systems in the right format. When something goes wrong, data does not disappear silently; the problem is noticed and the flow can be resumed where it stopped.

What is an API and why does it matter?

An API (Application Programming Interface) is the interface that defines which data and operations a piece of software opens to other software, and under which rules. Payment providers, shipping companies, marketplaces and many ERP and CRM programs offer this kind of interface. An API integration is the software layer that lets two systems talk through these interfaces.

Not every system’s API is of the same quality. Some offer current and well-documented REST interfaces, some work with older SOAP and XML services, and some offer no API at all. When planning API and system integrations, the first job is to check the status of each system to be connected from this point of view.

The hidden cost of moving data by hand

When there is no API integration between systems, the following problems become an ordinary part of the work over time:

• The same information being typed into two or three systems separately, with a chance of error at every entry.
• Stock, price or order status looking different across systems.
• Extra staff needed only for data entry as sales grow.
• Records being searched by hand to find the source of an error.
• The customer being given wrong or late information.

Which businesses is it meaningful for?

• Businesses that sell through more than one channel, such as a website, marketplaces and a physical store.
• Companies that keep stock and customer account information in an ERP but take orders in another system.
• Companies that regularly exchange data with their dealers, suppliers or partners.
• Organizations whose sales and customer service teams work in different software.

Common types of API integration

Every business has a different software map, but some types of connection are needed in most businesses. The headings below are the areas most often discussed under API and system integrations. We described the payment and shipping experience the customer sees on our e-commerce websites page; here, the subject is the data flow behind that experience.

Payment integrations

In a virtual POS or payment provider integration, the basic topics are not storing card details on your server, 3D Secure verification and reliably recording the payment result on the order. Methods where the payment form opens on the payment provider’s infrastructure, or where the card is represented by a token, greatly reduce the burden of card data security. Refund, partial refund and installment scenarios should also be handled from the start as part of the API integration.

Shipping integrations

Through an API integration with a shipping company, it is possible to create a shipment record, get a label and tracking number, and follow delivery status automatically. Writing the tracking number onto the order and notifying the customer reduces the “where is my package” questions that reach customer service. If you work with more than one shipping company, the choice of company can also be tied to a rule based on shipping region or volumetric weight (desi).

ERP and accounting connections

ERP and accounting programs such as Logo, Mikro or SAP are often the main source of stock, price, customer account and invoice data. The website, mobile app or dealer portal takes this data from the ERP and sends orders and collections back to it. In an API integration with an ERP, the most critical decision is which data flows in which direction and how often.

CRM connections

When leads from web forms, ad campaigns or messaging channels drop into the CRM automatically, the sales team sees all requests in one place. Passing the customer record to the ERP and invoicing side when a sale is completed is the continuation of the same chain of API integration. Requests collected by AI-powered assistants also reach the right team thanks to these connections.

e-Invoice, marketplaces and messaging services

Businesses in Turkey that want to automate e-Invoice and e-Archive invoice processes with software usually work with private integrators approved by the Turkish Revenue Administration; these integrators mostly offer an API for the software connection. For businesses that sell on marketplaces, synchronizing products, stock, prices and orders is another type of API integration that is often needed. Messaging services such as SMS, email and WhatsApp can be part of notification flows.

Stock consistency in multichannel sales

If you sell the same product on your website, on several marketplaces and in your store, a sale on one channel needs to be reflected in the stock on the other channels. When this reflection is delayed, a product you do not have keeps being sold on another channel. The frequency of stock updates, the request limits of marketplaces and the safety stock set aside for each channel should be considered together when designing this kind of API integration.

How does an API and system integrations project proceed?

Every API integration is a mapping job before any code is written. Connections built before it is clear what each system knows and what it should know can quickly turn into a structure that corrupts each other’s data. We run the work with these steps:

1. System inventory: We list the software you use, their versions, their API status and their technical owners.
2. Data flow map: We draw which data leaves which system and goes to which, and what event triggers it.
3. Source of truth decision: We set a single correct source for each of product, stock, price, customer and order data.
4. Field mapping: We document how the fields in the two systems correspond to each other, including differences in units, currency, tax and codes.
5. Development and testing: Where possible, we develop in the providers’ test environments, without touching real data.
6. Controlled launch: We first run the integration with limited data and open it to full scope once the results are verified.
7. Monitoring: After launch, we follow errors and alerts to watch that the flow is running healthily.

Why is the source of truth so important?

If the price of the same product can be changed in both the ERP and the e-commerce panel, one day the two systems show different prices and nobody knows which one is right. That is why a single owner system is set for each type of data; the other systems only read that data. No matter how well an API integration is written, it cannot work consistently without this decision.

Test environment and going live

Payment providers, and some shipping companies, usually offer test environments where you can try things out without making real transactions. On the ERP side, the safest way is to work on a copy of the live system. When testing an API integration, we try not only successful scenarios but also a declined payment, a missing address, an out-of-stock product and the same notification arriving twice.

Ready-made module or custom integration?

For common e-commerce platforms and accounting software, ready-made plugins or modules may exist for payment, shipping and marketplace connections. If your business rules are standard, these are a fast and affordable solution. If your pricing, warehouse structure or approval processes are non-standard, writing a custom API integration causes fewer problems in the long run than forcing a ready-made module. When planning API and system integrations, we evaluate these two options separately for each connection.

Technical principles for an error-free data flow

Making a connection is the easy part of the work; the real effort is designing what happens when things go wrong. The other system may not respond, the network may drop, the same notification may arrive twice. When API and system integrations are built with these situations in mind, the data flow becomes reliable.

Real-time or scheduled?

• Webhook: The other system notifies your system when an event happens, for example when a payment is received or a shipment is delivered. It is fast, but measures are needed to verify the incoming notification and make sure it is not lost.
• Scheduled polling: Your system asks the other side at set intervals whether there is a new record. It is used with systems that do not offer webhooks.
• Batch transfer: Large data sets are transferred in bulk at set times. It suits product catalog or price list updates.

These methods can be used together within the same API integration: for example, order and payment notifications flow in real time, stock updates at short intervals and catalog updates in a nightly batch.

Error handling and retries

When the other system temporarily does not respond, the request should not be lost; it should be put in a queue and retried at set intervals. Processing the same request twice, for example the same order reaching accounting as an invoice twice, is at least as harmful as losing data. That is why we identify each operation with a unique key and prevent a repeated request from being processed a second time.

Many APIs limit the number of requests that can be made in a given time and reject requests when the limit is exceeded. An API integration should be designed to run at a speed that respects these limits and should resend rejected requests after a suitable wait.

Logging and alerts

An API integration that breaks silently is more dangerous than having none, because everyone assumes the data is flowing correctly. We log when each transfer was made, its result and any error message. We suggest sending an alert to the relevant people when a certain error threshold is exceeded or when an expected transfer does not take place. Making these logs and transfer statuses visible through admin panels makes it easier for non-technical teams to notice a problem too.

Security

API keys and access credentials should be stored in secure configuration areas, not inside the code. Each API integration should be given only the permissions it needs; an access opened to read orders should not be able to delete products. In flows that carry personal data, which fields really need to be transferred should be questioned separately, and data that is not needed should not be moved at all.

Notifications that come from outside should not be trusted blindly either. That a webhook request really comes from the provider concerned should be checked with a signature or a shared secret key; otherwise an order that has not been paid for can be confirmed with a fake “payment received” notification.

Maintaining the integration

An API integration needs attention after it goes live, too. Providers release new API versions, shut down old versions after a certain date and change security requirements. A field change in your own systems can also affect the flow. For API and system integrations, following provider announcements, reviewing logs regularly and trying changes in a test environment are ongoing parts of the work.

Developing your own API

Sometimes the need is not to connect to existing systems but to open your own system to others. For your dealers to place orders, for a partner to pull your stock information or for your mobile app to reach the data, your system also needs to offer an API. This side of our API and system integrations service is API development.

When designing your own API, you first need to think about who will use it. The documentation, support and security needs of an API that only your own mobile app will use are not the same as those of an API that dozens of dealers will connect to with different software. Every endpoint opened to the outside turns into a commitment that has to be kept backward compatible for a long time.

These are the features we look for in a well-designed API:

• Clear documentation: What each endpoint does, which parameters it takes and which response it returns should be written down.
• Versioning: When the API changes, the systems using it should not break, and the old version should keep working for a transition period.
• Authentication: Who each client is and what it can access should be checked.
• Consistent error messages: When a request is rejected, the reason should be reported in an understandable way.
• Usage limits: A single client should be prevented from slowing down the system with excessive requests.

One of the widely used standards for API documentation is the OpenAPI Specification, developed under the OpenAPI Initiative. Definitions written with this specification can be read by both people and software; the teams that will use your API can generate documentation pages, test tools and client code from this definition.

Offering a test environment before opening your API to outside users lets the teams that will connect try it without touching live data. Giving access keys to each partner separately also makes it possible to shut down a single partner’s access when needed without affecting the others.

Scope, preparation and common mistakes

In API integration projects, the most important factor that sets the scope is the state of the other systems. Working with a well-documented API that has a test environment is very different from working with a system that has missing documentation and only a live environment. The scope is determined by these factors:

• The number of systems to be connected and the API quality of each.
• Whether the data flow is one-way or two-way.
• Whether historical data will be transferred.
• The complexity of the business rules: unit conversions, tax calculations, multiple warehouses.
• Expectations for monitoring, reporting and alerts.

What to prepare

• A list of the software you use, with versions and license information.
• For each system, the contact details of the software provider or the technical owner.
• If available, API documentation, test environment access and API key application processes.
• A short description of the transfers done by hand today: who moves which data where, and when?

Common mistakes

• Not setting the source of truth: When two systems can change the same data, inconsistency becomes unavoidable.
• Testing only the successful scenario: Integrations break most often on a connection outage, missing data and a repeated notification.
• Not setting up monitoring: Errors are noticed only when a customer complains.
• Not following provider changes: When the other side changes its API version, the integration can suddenly stop one day.
• Forgetting historical data: If the integration only moves new records, how old orders and customer records will be handled needs to be planned separately.
• Passwords embedded in code: When access credentials leak, all the connected systems are put at risk.

Frequently asked questions

Do we need to replace our current software for API and system integrations?

In most cases, no. If your current software offers an API, we connect to it directly; if it does not, alternatives such as database access, file transfer or additional modules offered by the provider are considered.

How long does an API integration take?

The time depends on the API quality of the other system, the direction of the data flow and the complexity of the business rules. Once the system inventory and data flow map are done, we share a realistic schedule.

What happens if the system we want to connect to has no API?

First, we look at whether other routes exist, such as data export, database access or file sharing. If there is no route at all, talking to the software provider or replacing the system are the options to consider.

How will we know when the integration returns an error?

A monitoring setup should be built that logs the result of every transfer and sends an alert to the relevant people when there is an error. This way, problems can be noticed before they reach the customer.

Is API integration secure?

When set up correctly, yes. Encrypted connections, securely stored access keys, granting only the permissions needed and not transferring unnecessary personal data are the basic security measures of an API integration.

Will the integration break if the other system changes its API?

It can. Following providers’ version announcements and adapting the integration to the new version on time is part of maintaining the integration.

Let’s connect your systems

Telling us which software you use and which data you move by hand today is enough of a starting point for the first call. Together we map your data flow and talk about which connection should be built first for your API and system integrations. You can reach us through our contact page.