Your CRM says the customer’s billing address is in Ohio. Your ERP says Nevada. Both were updated last week, by different people, and nobody can tell you which one the invoice run will use. Meanwhile a channel partner has spent six months asking to pull order status programmatically, and the only answer available is a nightly CSV on an SFTP server.
That is what an integration project actually looks like. Not a greenfield platform. A pile of systems that already exist and already disagree. The hard parts are contract design, failure handling, and the unglamorous business of talking to systems nobody wants to touch.
How to Evaluate an API Development and Integration Partner
API Design and REST Competence
Ask one question early: do you design the contract first, or generate endpoints off the database? A partner opening with an OpenAPI specification and schema design is thinking about consumers. A partner who scaffolds CRUD endpoints from tables has published your data model to the world, and every schema change becomes breaking.
Probe REST fundamentals. How do they version, and what triggers a major version bump? Why does cursor pagination beat offset on large mutable datasets? Can they explain idempotency keys, so a duplicate POST during a timeout does not create two orders? Do errors carry machine readable codes rather than prose a client must parse?
Authentication deserves the same scrutiny. OAuth 2.0 with scoped tokens, API keys where the threat model justifies it, mTLS for partner traffic. Ask how scopes map to your permission model, then ask about rate limiting: per client quotas, burst handling, and what a throttled consumer sees.
When GraphQL Is the Right Call
GraphQL earns its cost when many clients need different shapes of the same data, when mobile bandwidth makes over fetching expensive, or when you are federating several backends behind one graph. It adds cost without benefit when you have one web client, simple resource access, and a team that must now reason about query depth limits, N+1 resolvers, caching without HTTP semantics, and field level authorization. A good partner tells you when not to use it.
Third-Party Integration Realities
Vendor APIs go down. They change without notice. They rate limit you at the worst moment and their sandbox behaves differently from production. Ask how a candidate handles webhook delivery: signature verification, replay protection, idempotent processing, and what happens when your endpoint is down for an hour. Ask about exponential backoff with jitter, dead letter queues, and circuit breakers so one failing vendor does not take checkout with it. If a vendor offers no sandbox, plan for that early.
Legacy System Connectivity
This is where projects stall. The approaches, roughly in order of preference: wrap an existing SOAP service in a modern facade, use a documented vendor API, read at the database level through a defined view with change tracking, exchange files over SFTP where batch timing allows, reach IBM i or mainframe systems through program calls and data queues, and only when a system exposes no interface at all, drive the screen with RPA or scraping. RPA at the boundary is legitimate when the alternative is a multi year replacement. It is a bad answer when a real interface exists and nobody looked.
Architecture, Testing, and Who Owns It Afterward
Middleware and iPaaS platforms are worth it when you have many point to point connections, standard SaaS endpoints, and a team that will maintain flows without code. Custom code wins when transformation logic is complex, volumes are high, or licensing scales badly against usage. A partner with one answer is selling their comfort zone.
Event driven patterns and message queues decouple systems that should not fail together. Ask how they handle ordering, at least once delivery, and poison messages. Ask what observability looks like: correlation IDs across hops, structured logs, redacted payloads, and alerting on integration failure rather than server CPU. Ask about contract testing between producer and consumer. If the API is external facing, ask to see a developer portal they built. Settle maintenance ownership in writing.
Xcelacore: Both Sides of the Integration
Most integration work fails at the seam. The API is fine, but the application on the other end must change to consume it, and that is a different vendor with a different backlog. Xcelacore’s structure removes that gap. Its Platforms & Integrations practice covers Salesforce, Microsoft Dynamics 365, NetSuite, and payment systems, while its custom software development practice builds the applications those platforms connect to.
The result is a partner who can build the API, modify the system publishing it, and adjust the consumer calling it, without three way coordination calls. Supporting services round out delivery: cloud development and DevOps, QA testing and automation, e-commerce work across Magento, WooCommerce, and Salesforce Commerce, and cybersecurity testing.
Robotic process automation is the notable addition. When a legacy system truly exposes no interface, Xcelacore can automate the interaction rather than call the integration impossible. That is a last resort, but having it in house means the option gets evaluated honestly. The firm is based in Oak Brook, Illinois.
Best for: organizations that need the platforms and integrations work and the application changes on either end handled by one accountable team.
Perficient: Integration Strategy at Enterprise Scale
Perficient is a US digital consultancy headquartered in St. Louis. Its integration and API practice covers the full lifecycle rather than individual builds: current state assessment through structured workshops, integration platform architecture and reference standards, governance models defining who may publish what, and lifecycle management including developer portals and automated build, test, and deploy pipelines.
That suits a specific buyer. If you have dozens of integrations accumulated over a decade, no standards, and no clear owner, the first problem is not code. It is deciding what good looks like and getting the organization to follow it. Perficient sells that groundwork alongside delivery teams.
Best for: enterprises that need an integration operating model and roadmap, not just a set of endpoints.
Chetu: Broad Protocol Coverage and Vertical Depth
Chetu is a US headquartered custom software development firm with a dedicated API offering spanning REST, SOAP and XML, and GraphQL, plus third-party integration across payment gateways, shipping and logistics carriers, messaging providers, and analytics platforms.
The firm positions microservices work as converting legacy systems into service oriented architectures, the practical version of modernization most organizations actually buy. API consulting and protocol selection, testing (functional, load, and penetration), and ongoing monitoring are separate lines. Chetu works through industry specialized teams, which matters when your integration involves domain formats rather than generic REST calls.
Best for: companies wanting one vendor across a wide protocol and vertical range, including older SOAP and XML estates.
Orases: US Based Integration Consulting
Orases is a custom software development firm headquartered in Frederick, Maryland, and states its team is fully located in the United States. Its integration consulting practice connects accounting, CRM, content management, ERP, and reporting systems, plus data migration covering cleansing, normalization, and transformation.
The firm describes bridging legacy and modern systems while preserving historical data, usually the constraint that makes these projects hard. Nobody objects to the new system. They object to losing twelve years of records in the move. Onshore delivery is a real differentiator for regulated buyers and teams burned by timezone gaps at cutover.
Best for: mid market organizations with onshore requirements and a mix of business systems to connect.
Velvetech: API Development with Chicago Roots
Velvetech is a custom software firm with offices in Chicago, Illinois, and Sunny Isles Beach, Florida. Its API services cover REST, GraphQL, SOAP, and RPC, microservices architecture, and third-party integration, with explicit categories for public, partner, internal, and composite APIs.
That last distinction is a useful signal. A firm separating partner APIs from internal ones is thinking about audience, versioning obligations, and support burden differently for each, the reasoning you want before a contract is drafted. Named targets include enterprise applications, cloud services, legacy software, IoT, SaaS platforms, and payment systems, across healthcare, insurance, transportation, manufacturing, and fintech.
Best for: teams that want API strategy consulting and build capacity from the same vendor.
Apriorit: Security First and Undocumented APIs
Apriorit is a software engineering firm whose API practice is framed around security throughout. The stack spans REST, SOAP, gRPC, and GraphQL, with third-party integration across cloud platforms, payments, authentication, and geolocation services.
The distinguishing capability is stated plainly on their site: integrating legacy and undocumented APIs using reverse engineering. Most vendors need documentation. When you face a system whose protocol nobody can explain and whose developers are long gone, that experience is a genuinely different tool. Testing is its own line, covering performance, load, and security rather than functional checks alone.
Best for: integrations where the target system is poorly documented, or where API security is the primary risk.
Belitsoft: Industry Specific API Work
Belitsoft’s API practice is organized by vertical rather than technology, which shows in what they name. Healthcare covers HL7, FHIR APIs, EHR integration, and HIPAA-oriented delivery. Logistics covers TMS and WMS connectivity plus EDI replacement. Manufacturing covers ERP integration, and HR covers connectors like BambooHR.
On the technical side they describe REST design spanning endpoints, HTTP methods, data formats, and authentication, plus GraphQL, webhooks (consuming and building them), and integration with modern and legacy systems. AWS API Gateway and Azure API Management appear as named platforms. Vertical framing matters because most integration cost lives in the data model, not the transport.
Best for: healthcare, logistics, or fintech integrations where standards and compliance shape the design.
Daffodil Software: Protocol Breadth and API Management
Daffodil Software offers custom API development across REST, SOAP, XML, JSON, and gRPC, with gRPC positioned for low latency scenarios. A firm naming gRPC deliberately is thinking about service to service performance rather than defaulting to HTTP JSON everywhere.
Integration coverage includes payment gateways, shipping carriers, cloud communication platforms, IoT data exchange, and ERP and CRM systems. The management side adds API consulting and strategy, API as a service, automated load, functional, and unit testing, and ongoing support. They also categorize public, partner, internal, and composite APIs, so contract design precedes implementation.
Best for: teams needing a wide protocol range plus lifecycle management and testing under one engagement.
Softura: GraphQL Gateways Over Existing Services
Softura is headquartered in Farmington Hills, Michigan, with additional North American and international offices. Its GraphQL practice covers API development, integrating GraphQL into an existing stack through gateway APIs, and manual and automated testing through CI/CD pipelines.
The gateway framing is the interesting part. Most organizations do not replace REST services with GraphQL. They put a graph in front of what exists so client teams stop writing five calls where one would do. A partner who describes the work that way is solving the actual problem. Softura also offers application modernization, cloud enablement, AI, business intelligence, and IoT work.
Best for: organizations adding a GraphQL layer over existing services rather than starting from scratch.
United Techno: iPaaS Specialists
United Techno focuses on integration platform as a service delivery across Boomi, MuleSoft, Workato, Celigo, and hybrid multi-cloud setups. The offering splits into strategy and architecture (API led design and governance), enterprise integration delivery, and managed operations including monitoring and support.
Platform neutrality is worth something. A partner certified on one tool will recommend that tool. A partner working across several can tell you when your volume and transformation complexity make licensed middleware more expensive than custom code. Managed operations matter too. Integrations need someone watching at 2am when a vendor rotates a certificate.
Best for: organizations standardizing on an iPaaS platform, or unsure which one fits.
Making the Choice Practically
Do the scoping before you request proposals. Vendors quote what you describe, and vague descriptions produce quotes that change once discovery starts. Fill this in first:
- Systems involved. Every system, its version, its vendor, and whether it is on-premise or SaaS. Flag the ones you cannot modify.
- Direction of data flow. One way or bidirectional, per entity. Customers might sync both ways while invoices move one direction.
- Volume and frequency. Records per day at peak, not average. Real time, hourly, or nightly batch.
- Latency tolerance. How stale can the receiving copy be before someone makes a bad decision? Answer in minutes, not “as fast as possible.”
- Error handling. Who gets notified, what retries automatically, and what needs human intervention.
- Who owns the data of record. For every shared field, one system wins conflicts. That is a business decision, not a technical one.
- What happens during an outage. Queue and replay, fail fast and alert, or degrade to manual. Each implies a different architecture and cost.
Bring that document to three vendors. The ones who push back on your assumptions are worth shortlisting. Run a paid discovery or a small first integration before committing to the full program. For a partner who can also change the applications on either end, review Xcelacore’s platforms and integrations services.
Disclaimer
This list reflects the opinion of the author and appears in no particular order. It is not a ranking, and inclusion does not imply endorsement. Evaluate any provider against your own requirements before engaging them.
