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Web applications rarely exist in isolation. They pull data from CRMs, push events to analytics platforms, sync records with ERPs, trigger notifications via messaging services, and expose their own APIs for consumption by mobile apps, partners or other internal systems. Building these integrations correctly — with proper error handling, retry logic, security and observability — is what separates production-grade applications from fragile ones. At Hellenic Technologies, API integration work is treated as first-class engineering. We design integration layers that are testable, maintainable and resilient to the failures that inevitably occur when your application depends on third-party services.

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Integration Patterns We Implement

  • REST API consumption — Authenticated calls to third-party REST APIs with proper token management (OAuth 2.0, API key rotation), rate limit handling, and response caching where appropriate
  • GraphQL — Query-based integrations with GraphQL APIs for efficient data fetching; also our preferred API design for new internal APIs
  • Webhooks (inbound) — Receiving and processing events pushed by third-party services (payment confirmations, CRM updates, form submissions); includes signature verification and idempotent processing
  • Webhooks (outbound) — Publishing events from your application to subscriber endpoints; retry queues, delivery status tracking, and subscriber management
  • Background job queues — Long-running API operations (bulk imports, report generation, third-party sync) handled as background jobs to avoid request timeouts; implemented with Laravel Queues or Bull (Node.js)
  • API gateway and rate limiting — For applications exposing their own API: authentication, rate limiting, usage logging and versioning

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Specific Integrations We’ve Built

  • Payment processors: Stripe, Viva Wallet, PayPal
  • CRM: HubSpot, Salesforce, Pipedrive
  • Email: Resend, Postmark, Mailchimp, SendGrid
  • SMS: Twilio, Vonage, local Greek SMS providers
  • Greek services: GSIS (tax authority), AADE e-invoicing (myDATA), IANOS
  • Shipping and logistics: ACS, ELTA, DHL, Speedex
  • Authentication: Google OAuth, Microsoft Azure AD, Auth0
All integrations are covered by integration tests that run against sandbox environments in CI, so a third-party API change does not silently break production.