Viacheslav Kostin
CEO WislaCode Solution
Ready to develop something unique?
Let's start the conversation and develop your own unique project.
API Integration Services
Build a connected architecture instead of a patchwork of systems. With robust API integrations, your products communicate reliably, data flows stay synchronised, and your teams operate from a single, trusted source of truth.
Why it matters
If you’re scaling fast, fragmented systems and manual data flows kill velocity.
Our team designs and delivers secure, production‑grade integrations that eliminate silos – connecting banking, payments, KYC/identity, CRM/ERP, logistics, and analytics layers through well‑documented, testable APIs.
At WislaCode, we don’t sell middleware boxes – we engineer integrations aligned with your architecture, security model, and product roadmap. Vendor‑agnostic, compliant, and built to evolve with your stack.
Third‑party integrations that just work
We connect your product to payment gateways, KYC/identity providers, CRM/ERP systems, logistics, analytics, and social platforms – the real backbone of digital ecosystems. Our integrations are engineered for reliability: clean contracts, signed webhooks, idempotent operations, retry logic, and graceful rate‑limit handling. Data stays in sync, and external API issues don’t break your user journeys.
Mobile‑first APIs for iOS and Android
Designed for real‑world conditions: low latency, limited bandwidth, and offline scenarios. We optimise payloads, support background sync, and ensure backward compatibility across app versions. Security is baked in with OAuth/OIDC, token management, and encryption best practices.
Custom APIs built for your domain
We design and implement REST or GraphQL APIs around your data model and workflows – not the other way round. Each API includes strong authorisation, versioning, pagination, and mapping to keep integrations predictable. You get production‑ready documentation, SDKs where they add value, and a developer‑friendly interface that’s easy to maintain.
Cloud‑ready and serverless architectures
We build APIs that scale and remain observable – autoscaling, cost‑optimised, and compliant from day one. Using IaC, CI/CD pipelines, zero‑downtime deployments, and robust secret management, we ensure every service remains secure, maintainable, and ready for growth.
Core capabilities in API integration
SCA‑ready card and wallet flows with 3‑D Secure, tokenisation, webhooks, and reconciliation. PCI DSS / PSD2 compliant, with clear dispute handling and settlement logic.
Two‑way sync with deduplication, conflict resolution, batching, pagination, and rate‑limit management. Customer, order, and inventory data stay consistent.
Signed payloads, idempotent processors, retries with exponential backoff, and dead‑letter queues. Event‑driven setups that remain stable and observable under load.
SOAP‑to‑REST adapters, mapping and authentication bridges, incremental migration using the strangler‑fig pattern. Legacy endpoints stay operational while new services roll out.
How API integrations are delivered step by step?
Define scope, dependencies, and data flows. Select external providers, outline contracts, and assess risks before implementation.
Planning
Analysis
Run functional, integration, and load tests in staging environments. Validate security, performance, and backward compatibility.
Testing
Design predictable interfaces and map data models. Implement endpoints, auth, error handling, and monitoring hooks from day one.
Design
Development
Deploy gradually with telemetry and rollback options. Document endpoints and edge cases; support internal teams during adoption.
Launch
Support
Case: Powering a fitness PWA with a resilient API‑first backend
A fitness club network needed an accessible app for self‑guided workouts. We partnered from discovery to delivery, building the server‑side services and clean API layer powering a progressive web app. Secure authentication, workout plan storage, progress tracking and well‑versioned endpoints supported rapid front‑end iteration. We introduced rate limiting, caching and observability to keep performance predictable.
Result: first release in four months; ongoing adoption with 81% of members using the app. The backend remains reliable and easy to evolve as features expand.
Why WislaCode?
We integrate payments, identity, CRM/ERP, logistics and analytics without locking you to one provider. The solution serves your product, not a single roadmap.
Vendor‑agnostic integration expertise
OAuth/OIDC, least‑privilege keys, encrypted data paths and audited actions are built in. We align with GDPR and PCI/PSD2 where relevant, with evidence surfaced via CI/CD.
Security and compliance as a habit
Timeouts, retries, idempotency and circuit breakers are standard. Metrics, logs and traces reveal issues fast, while canary rollouts and clear rollback keep releases safe.
Resilience and observability by design
Engage an end‑to‑end team or hire API integration developers to augment your squad. We track KPIs – sync latency, error budgets, data freshness and share progress openly.
Flexible engagement, transparent outcomes
FAQ about API integration
iPaaS speeds simple workflows, but complex products need fine‑grained control over data models, error semantics and performance budgets. Dedicated API integration developers design clean contracts, implement resilience (retries, idempotency, back‑pressure) and wire observability so issues are visible, not mysterious. Many teams combine both: iPaaS for low‑risk glue, custom integrations for core journeys and scale. We help you choose pragmatically and avoid platform lock‑in.
We separate concerns: authentication via OAuth/OIDC with short‑lived tokens, payments through providers with 3‑D Secure and tokenisation. Sensitive data avoids your servers where possible. Webhooks are signed, verified and idempotent, reconciliation jobs keep ledgers accurate. We enforce least‑privilege API keys, rotate secrets, and run threat modelling plus pen tests before launch, aligning with PCI practices and PSD2/SCA requirements.
Start with a clear data contract and ownership. We implement staged imports, deduplication, conflict rules and pagination to respect rate limits. Event‑driven updates keep systems fresh, scheduled reconciliations correct drift. Mappings and edge cases are documented, dashboards show sync latency and error classes. This approach reduces surprises and keeps sales, service and finance working from consistent, trustworthy data.
We validate signatures, record payloads and use idempotency keys to prevent duplicates. Consumers apply exponential backoff and move failures to dead‑letter queues for investigation. Parallelism is controlled to protect downstream services, dashboards show delivery rates and error patterns. Runbooks cover replay and partial reprocessing. The result is predictable, auditable event processing – even when providers throttle or spike.
Yes. We place an adapter layer that translates SOAP to REST/GraphQL, normalises payloads and bridges authentication. New consumers talk to the adapter while we gradually migrate underlying calls, a strangler‑fig pattern. Compatibility tests and shadow traffic de‑risk cut‑over. Over time, legacy endpoints are retired as new services assume responsibility, avoiding big‑bang rewrites and service interruptions.
Discovery and design: 1–2 weeks. Prototyping and risk spikes: 1–3 weeks. Core implementation: 3–6 weeks per integration (often in parallel). Hardening and staged release: 2–3 weeks. Timelines vary with provider maturity, auth complexity and volume. We provide a clear plan, KPIs (latency, error rates, data freshness) and rollout strategy and you can scale capacity by hiring API integration developers from our team when needed.
Viacheslav Kostin, CEO
20+ years of experience in managerial positions in IT and banking.
Viacheslav Kostin, CEO
Previous roles: CEO in IT, Director of Strategy and Marketing in Banking, Curator of Holding Banks, Head of Products and Project Office.
Education: MBA for Executives at IMD (Switzerland), Leading Digital Business Transformation (IMD). Provides consulting in strategy and digital transformation.
Vasil Pahomov, CTO
20+ years of experience as a developer, analyst, and solutions architect.
Vasil Pahomov, CTO
Designs resilient, high-load systems with multiple integrations for banks and financial institutions. Expertise in distributed storage and microservices architecture.