Secure APIs That Connect Your Systems.
API development, third-party integrations, automation engineering and data sync architecture. Built for reliability, not just connectivity, with OWASP security compliance and full monitoring from day one.
What is API and Integration Engineering?
API and integration engineering is the discipline of designing, building and maintaining the connections between software systems so that data flows accurately and automatically between the tools a business depends on. It covers custom API development (RESTful and GraphQL), third-party platform integrations (CRM, ERP, payment gateways, marketing platforms), webhook architecture for real-time event-driven data flows, automation workflows that trigger actions across systems, and data migration pipelines for one-time or ongoing synchronisation between databases. A well-engineered integration layer eliminates manual data entry, removes the operational risk of human error in data handoffs and creates a single accurate version of business data accessible across every system in the stack.
Signs You Need Integration Engineering
- Your team is manually copying data between your CRM, ERP, billing system and marketing platform on a daily or weekly basis, creating delays and data quality errors that compound over time.
- Your Zapier or Make automation is silently failing on a subset of records, and you only discover data loss after a customer complaint or a revenue discrepancy that takes hours to trace.
- You are building a new product or platform that needs to expose data to partners or integrate with systems your customers already use, and you need a secure, documented API to make that possible.
- You are migrating from one system to another (CRM, ERP, commerce platform) and need to move years of data accurately, with validation and without disrupting live operations during the transition.
- Your operational reporting is unreliable because the same data entity has different values in different systems and there is no integration layer enforcing a single source of truth.
Who This Is For
SaaS Companies Building a Partner Ecosystem
Software companies that need to expose their platform data to partners and customers via a secure, documented public API, or build native integrations with the tools their customers use to drive adoption and reduce churn.
Scale-Up Operations Teams
Companies that have grown past the point where manual data transfer or fragile no-code automation is acceptable, and need reliable, monitored integration infrastructure connecting their CRM, finance, operations and marketing systems.
Businesses Undergoing System Migration
Companies replacing a core system (CRM, ERP, commerce platform or billing tool) who need data migration architecture that preserves data integrity, validates every record and maintains business continuity throughout the transition.
Product Teams Automating Revenue Operations
RevOps, sales and marketing operations teams who need reliable automation connecting their CRM, outreach, billing and analytics tools so that lead routing, deal progression and customer lifecycle events are handled without manual intervention.
What You Get
- RESTful or GraphQL APISecure, documented API built to your data model with authentication, rate limiting, versioning and OpenAPI specification delivered as a standard deliverable.
- Third-Party System IntegrationsCRM, payment gateway, marketing platform, ERP and accounting integrations with bidirectional data flow, transformation logic and field mapping documented for each connection.
- Webhook ArchitectureEvent-driven real-time data push between systems triggered on business events, with payload validation, retry logic and delivery confirmation so no event is silently dropped.
- Data Migration PipelineOne-time or ongoing sync pipelines with data quality validation, transformation rules, rollback capability and a post-migration reconciliation report confirming record accuracy.
- Automation Workflow EngineeringMulti-step automation workflows built in Make, n8n or AWS Lambda for business event handling, lead routing, order processing and operational triggers across connected systems.
- API DocumentationOpenAPI specification, endpoint reference with request and response examples, authentication guide and integration runbooks so your team can maintain what we build.
- Integration Monitoring and AlertingStructured logging, failure alerting and a monitoring dashboard covering sync success rate, latency and data volume across all integration points from launch.
- Security ReviewOWASP API Security Top 10 review before production deployment, covering authentication, injection vulnerabilities, rate limiting, sensitive data exposure and access control.
What We Connect
RESTful and GraphQL APIs
Secure, documented API endpoints built to your data model. Internal APIs connecting your own services, and external APIs exposing your platform to partners, customers and third-party developers.
Third-Party Integrations
CRM, payment gateway, marketing platform, ERP and accounting integrations. Connect your full stack without manual data transfer, with field mapping, transformation logic and error handling built in.
Webhook Systems
Event-driven architectures with real-time data push between systems on business triggers. Delivery confirmation, retry logic and dead-letter queues so no event is lost or processed twice.
Data Sync Architecture
One-time data migrations and ongoing sync pipelines with a single validated source of truth across all systems. Bidirectional sync where required, with conflict resolution rules defined upfront.
The Koldconvert System Unification Framework
Most integration projects fail not because the connection cannot be built but because nobody mapped what data should move, in which direction, under what conditions and with what logic applied when the upstream system changes its schema or rate limits its API. The Koldconvert System Unification Framework starts every engagement with an integration dependency map: every system, every data entity, every existing handoff, manual or automated. From that map we design the integration architecture with failure modes as a primary concern, not an afterthought. Every integration we build has error handling, retry logic, structured logging and an alerting system configured before production deployment. We do not consider an integration complete until it is observable, because an integration you cannot monitor is an integration you cannot trust.
From Systems Audit to Live Integration
Systems Audit
Map all current systems, data flows and integration gaps. Produce a dependency map showing what data lives where and what manual handoffs need to be automated.
Integration Design
Architecture design covering authentication approach, data models, transformation rules, error handling strategy and sync frequency. Reviewed and approved before build starts.
Build and Test
Integrations built against sandbox environments with comprehensive testing including edge cases, failure scenarios and load conditions. Data integrity validated before production.
Deploy and Monitor
Live deployment with structured logging, failure alerting and a monitoring dashboard. Full API documentation and integration runbooks delivered. Post-launch support window included.
Tools & Technology
Make and n8n handle visual workflow automation for mid-complexity integration logic without requiring a full serverless deployment. AWS Lambda runs stateless integration functions at scale with event-driven triggers. REST and GraphQL APIs are built code-first with OpenAPI documentation generated automatically. Segment and Fivetran handle event streaming and data pipeline work into data warehouses. HubSpot and Salesforce APIs are connected using their native SDKs with OAuth 2.0 authentication and webhook subscriptions for real-time event handling.
How We Work Together
Single Integration Build
A defined-scope engagement to connect two systems with a reliable, documented integration. Includes systems audit, build, testing, monitoring setup and documentation. Suited to specific pain points with a clear input and output. Typical duration: 2 to 4 weeks.
Full Stack Integration Architecture
End-to-end integration architecture connecting your entire business stack: CRM, ERP, billing, marketing and analytics. Includes dependency mapping, architecture design, phased build and full monitoring infrastructure. Typical duration: 6 to 12 weeks.
Integration Maintenance Retainer
Ongoing monthly engagement covering integration monitoring, upstream API change management, new integration builds as your stack evolves, and incident response when integrations fail under real operating conditions.
What Clients Achieve
Integration Results
Integration Engineering for Your Industry
FinTech & Payments
Open banking API connections, payment gateway integrations with reconciliation logic, KYC provider webhooks and real-time fraud signal routing between detection systems and transaction processors.
HealthTech & MedTech
HL7 and FHIR-compliant health data integrations, EHR system connections, patient data sync with GDPR and data residency controls, and wearable device data pipeline architecture.
E-commerce & Retail
Shopify to ERP order sync, inventory level webhooks to prevent overselling, 3PL fulfilment API connections and customer data unification between storefront, CRM and email platform.
SaaS & B2B Software
Public API development for partner integrations and marketplace listings, CRM-to-product usage data sync for health scoring, billing platform webhooks and customer data platform connections for product analytics.
Logistics & Supply Chain
Carrier API integrations for real-time shipping rates and tracking, WMS-to-ERP sync for inventory accuracy, EDI translation layers for legacy supplier systems and customs documentation automation.
EdTech
LMS API integrations with SCORM and xAPI compliance, student data sync between learning platforms and SIS systems, payment gateway to enrolment automation and progress reporting pipelines.
HR Technology
HRIS-to-payroll integration with data validation at each transfer, employee provisioning webhooks to identity management systems, and benefits platform connections with real-time eligibility sync.
InsurTech
Policy management system integrations, claims API connections to loss adjustment platforms, telematics data ingestion pipelines and reinsurance data exchange with transformation and validation logic.
Legal Tech
Matter management system integrations, document automation pipeline connections, e-signature platform API integration and client portal data sync with DMS and billing systems.
Energy & CleanTech
Smart meter data ingestion APIs, grid management system connections, carbon accounting data pipelines and renewable energy certificate trading platform integrations.
Manufacturing & Industry 4.0
MES-to-ERP data integration, machine telemetry API ingestion, supplier EDI modernisation from legacy formats to REST APIs and quality management system event-driven automation.
Marketplaces & Platforms
Webhook-driven seller and buyer event handling, payment split and payout automation, fraud signal integration from third-party providers and external review platform data aggregation.
Koldconvert vs No-Code Automation Tools
| Factor | Koldconvert | No-Code Automation (Zapier / Make) |
|---|---|---|
| Data volume handling | Code-level integrations handle any volume without rate limits or task caps | Task and operation limits create bottlenecks under real business volume |
| Error handling | Retry logic, dead-letter queues and failure alerts built into every integration | Silent failures that skip records without alerting you to data loss |
| Monitoring | Full observability stack: structured logs, dashboards, alerting from launch | Platform UI only, no custom alerting, no integration with your ops tooling |
| Security | OWASP compliance, token storage review, API security audit before production | Credentials stored in the platform with no independent security review |
| Documentation | OpenAPI spec, endpoint reference and integration runbooks as deliverables | Visual workflow diagrams only, impossible to hand over or audit properly |
| Dependency risk | Code runs in your own infrastructure with no third-party platform dependency | Pricing changes, outages or plan removals at the platform level break your operations |
| Complexity ceiling | No ceiling: any logic, any transformation, any number of systems | Hits a complexity ceiling where workarounds create new fragility |
The integration debt problem in B2B companies is almost always invisible until it becomes a crisis. A business running on ten systems with no reliable integration layer is not running on ten systems: it is running on ten systems plus an unknown number of manual processes and workarounds that exist in people's heads, not in any documentation. That invisible layer carries enormous operational risk. Every employee who understands a manual data handoff is a single point of failure. Every Zapier workflow that silently drops a record is corrupting a database that reporting teams are trusting. Integration engineering is not a technology project: it is risk management for a business that has grown faster than its operational infrastructure. We treat it that way.
Koldconvert Strategy Team
Questions to Ask Any API and Integration Partner
- How do you handle upstream API changes after the integration goes live? APIs change: endpoints deprecate, schemas evolve, rate limits shift. A strong answer describes a monitoring process that catches breaking changes before they affect your data and a maintenance model for keeping integrations current.
- What happens when an integration fails and how will we know? The answer should describe specific alerting (not just "we monitor it"), retry logic for transient failures, a dead-letter queue for records that cannot be processed, and a support SLA with defined response times.
- Can we see the documentation you deliver for an integration you have already built? Documentation quality reflects how seriously a partner takes maintainability. You should receive an OpenAPI spec, endpoint reference and runbook, not just a verbal explanation. An agency that cannot show you documentation from a previous project probably does not produce it.
- What security review do you conduct before an integration goes live? The answer should name specific checks: OWASP API Security Top 10, OAuth token storage review, rate limiting configuration and input validation. If security review is described as optional or "we do our best," that is insufficient for any integration handling sensitive business data.
- How do you validate that the data transferred matches the source after a migration? A credible answer describes record count reconciliation, field-level data quality checks and a post-migration report you can review before signing off. Trusting that a migration worked without evidence is how organisations discover data loss three months later.
Glossary
- REST API
- A REST (Representational State Transfer) API is a web API that uses standard HTTP methods (GET, POST, PUT, DELETE) to expose data and functionality over the internet, following a stateless request-response architecture where each call contains all information needed to process it, making it the dominant integration pattern for modern business software.
- Webhook
- A webhook is an HTTP callback that sends data to a receiving system automatically when a specific event occurs in the source system, enabling real-time event-driven integration without polling, for example a payment gateway sending an order confirmation event to your CRM immediately when a payment succeeds.
- OAuth 2.0
- OAuth 2.0 is an industry-standard authorisation framework that allows a system to access resources in another system on a user's behalf without exposing credentials, using short-lived access tokens and refresh tokens instead, and is the authentication method required by most modern business APIs including Salesforce, HubSpot and Google Workspace.
- Idempotency
- Idempotency in API design means that making the same API call multiple times produces the same result as making it once, preventing duplicate records or double-charges when network failures cause requests to be retried, critical for payment and order-creation endpoints where duplicate processing has direct financial consequences.
- ETL Pipeline
- An ETL (Extract, Transform, Load) pipeline is a data integration process that extracts data from a source system, applies transformation rules to clean, validate and reformat it, then loads it into a destination system or data warehouse, used for data migration projects and ongoing synchronisation between systems with different data models.
- Rate Limiting
- Rate limiting is a control applied to an API that restricts how many requests a client can make within a defined time window, protecting the server from overload and ensuring fair usage across multiple consumers, requiring integration code to implement backoff and retry logic to handle 429 responses without losing data.
API and Integration, Answered
RESTful APIs, GraphQL APIs and webhook systems. Internal APIs connecting your own services, external APIs exposing your platform to third-party partners and customers, and integration APIs bridging existing systems that were not designed to communicate with each other.
CRM systems including HubSpot and Salesforce, payment gateways including Stripe, marketing platforms including Klaviyo and ActiveCampaign, ERP and accounting software including Xero and QuickBooks, and any platform that exposes a public API or webhooks. We have not yet encountered a system we could not connect.
All APIs are built with authentication via OAuth 2.0 or API keys, rate limiting, input validation and encrypted data transmission. We follow OWASP API Security Top 10 guidelines and conduct a security review before any integration goes live in production.
Yes. Data migration architecture and one-time or ongoing sync pipelines are standard integration work. Migrations are designed to be reversible, validated against a data quality checklist and non-disruptive to live operations. A post-migration reconciliation report is delivered as standard.
A simple integration or single API endpoint takes 2 to 4 weeks. A full integration architecture connecting multiple systems takes 6 to 12 weeks. Timeline depends on the number of systems, data volumes, transformation complexity and authentication requirements.
A single third-party integration typically ranges from £3,000 to £12,000 depending on API complexity and data transformation requirements. A full integration architecture connecting multiple systems ranges from £15,000 to £60,000. We scope accurately on the discovery call before any commitment.
No-code tools are appropriate for low-volume, simple data flows between popular platforms where the risk of data loss is low. Custom development is required when data volumes exceed what no-code tools handle reliably, when the logic is complex, when you need guaranteed delivery with retry logic, or when the integration is business-critical and cannot tolerate silent failures.
Yes. Automation engineering covers triggered API calls on business events through to multi-step orchestration workflows using Make, n8n or custom AWS Lambda functions. Automation is treated as a category of integration work, not a separate service, because the reliability requirements are identical.
Yes. Migrating brittle no-code automation to production-grade custom integrations is a common engagement. We audit your existing automation landscape, identify which flows are causing data quality problems, and rebuild them with proper error handling, logging and monitoring.
Every API is documented with an OpenAPI specification, endpoint-by-endpoint request and response examples, error code reference and an authentication guide. Integration runbooks are provided for every third-party connection so your internal team can understand and maintain the integrations without depending on us indefinitely.
FinTech, HealthTech, SaaS, logistics, e-commerce, HR technology and any sector operating multiple software systems that need to share data reliably. Integration complexity scales with the number of systems and the business criticality of the data moving between them.
Koldconvert treats integration engineering as a system discipline, not a one-off connection task. Every integration is designed with error handling, monitoring and documentation from the start. A freelancer typically builds the happy path. We build for the failure modes, edge cases and upstream API changes that happen six months after launch.
Ready to connect your systems?
Book a call to discuss your integration requirements and get a scoping estimate before any commitment.