Roadmaps slow one workaround at a time, with every release paying the tax of an API contract that was never designed for change. Relevant Software builds APIs that keep your roadmap fast: contracts agreed before code, versions that don’t break what already runs, and documentation that keeps delivery speed independent of who wrote the original build.
Architecture decisions get made before code does: resource models, protocol choice, versioning policy, and service boundaries, laid out for your team’s review.
Custom API development covers the full build — resource models, endpoints, authentication, and error handling — implemented against the contract your team approved.
Integration connects the APIs you build or already run with the CRM, payment, logistics, and SaaS platforms around them, so data moves between systems without manual re-entry; full-scale programs of this work are delivered through our API integration services.
Protocol choice follows the consumer: REST for broad compatibility, GraphQL where clients shape the data, gRPC for service-to-service speed — one team covers all three.
These are the endpoints behind the screens: backends purpose-built for the web development and mobile app development work they power, shaped to each client platform.
Cloud-native builds run as managed, autoscaling services on AWS, Azure, or GCP — the same serverless and container patterns our cloud application development work relies on.
Aging SOAP services and undocumented endpoints get rebuilt into documented REST or GraphQL contracts without breaking existing consumers; if the system behind them needs the same rework, it is scoped as application modernization.
Every external contract ships with authentication, authorization, rate limiting, and audit logging designed in, then goes through penetration testing before release.
Contract, load, and failure tests run in CI as part of quality assurance, so a breaking change fails the build rather than a client.
Documentation ships together with the API: reference docs, code samples, and sandbox access packaged where your engineers already work.
Data APIs put the outputs of data engineering work — pipelines, warehouses, real-time streams — behind stable contracts, so products consume data without touching the plumbing.
Your systems, consumers, and constraints go through a short discovery; the output is an architecture blueprint and a scoped plan your stakeholders sign before any build starts.
The OpenAPI or schema specification lands with your team first, so naming, resource models, and error semantics get debated on paper — where changes are cheap.
Each sprint closes with endpoints you can call against staging, so progress stays verifiable through the whole build.
Load and failure testing runs in a staged environment against your projected peak, so the weak points surface before launch; the suite stays in your pipeline afterward.
Deployment goes out in stages with dashboards, alerts, and dependency health in place from the first request.
Documentation, runbooks, and recorded walkthroughs transfer to your engineers, with a support window matched to how critical the API is.
ISO 27001, GDPR, and HIPAA-aligned delivery. Security review and audit logging are part of the build plan from the first sprint, so the API passes procurement the first time.
Relevant AI Delivery Framework™: up to 50% faster delivery and up to 20% fewer bugs through AI-assisted development — with every release still passing senior code review.
99% of milestones delivered on time. The contract-first process removes the usual source of slippage: rework after the build meets its consumers.
96% employee retention. The people who design your API contract are still on the account when version three ships, so domain knowledge accumulates instead of resetting with each handoff.
Open Banking, HL7 FHIR, and PSD2 deliveries mean the compliance questions in fintech and healthcare get answered from delivery experience.
200+ companies have built and scaled products with Relevant — the case studies below are the checkable subset.
The market range is wide — roughly $5,000 for a simple internal API to $50,000+ where compliance is involved — because the price follows a handful of variables: the number of resources and endpoints, the auth complexity (API keys vs full OAuth with roles), the compliance regime, how many consumer teams the contract must serve, and whether legacy systems constrain the design. Relevant reviews these five variables with you on the initial call. The proposal you receive itemizes each one, so you see exactly what drives your number.
A focused API is typically 3–6 weeks; a customer-facing API with auth, documentation, and load testing runs 6–12; complex or compliance-bound builds go longer. The schedule risk is front-loaded: projects that skip discovery extend timelines by 30–50%, because the contract gets redesigned mid-build.
One check you can run today: if nobody can name the API’s consumers and their read/write patterns, discovery has not happened yet — whoever builds it. With the contract-first process, your teams start building against the reviewed specification weeks before the implementation is finished.
No, and pricing them as the same thing is how scopes go wrong. The simplest way to tell them apart: development builds software you don’t have yet — a new capability, endpoints for your product or your partners. Integration makes the tools you already pay for share data — for example, orders that today get re-typed from one system into another.
If the goal is new functionality, you need development; if the goal is to stop copying data between existing systems, you need API integration. Mixed cases are common, and the two tracks run side by side under one architecture owner. And if you are still unsure which one describes your situation, feel free to contact Relevant Software — the team will help you define the scope before any commitment.
Usually, yes — and an audit answers it precisely. The first pass maps what exists: endpoints, consumers, auth, test coverage, and the gap between documented and actual behavior. From there the work is incremental — the current behavior gets pinned with tests, then the parts that need rework migrate step by step while the old version keeps running.
A check you can run this week without pulling anyone off delivery: ask whoever owns the API today for its documentation and for the list of teams and applications that use it. If either takes more than a day to appear, the real gap is knowledge — and knowledge gaps are recoverable without paying for a rewrite.
Both are right about different problems. Count the round-trips: if key screens assemble data from four or five REST calls today, GraphQL removes real latency and real code. Then ask who will own the graph — GraphQL centralizes schema decisions, which is a benefit with a clear owner and a bottleneck without one. REST stays the default for public and partner-facing contracts because every tool on earth speaks it. Many production systems land on both: GraphQL inside for product screens, REST outside for partners — the decision is made per consumer.
Three things get designed in from the first sprint:
Before signing any vendor, ask to see audit-trail output from a past build — the artifact itself. For clinical data exchange specifically, an implementation of HL7 FHIR gives you the contract the rest of the healthcare ecosystem already speaks.
The signal is ownership. If your engineers will own the API and need reinforcement — a contract designer, a security review — specialists embedded in your process work best. If the API is new territory and you want delivery owned end to end, a dedicated team carries architecture through support while your team stays on product. A quick test: who answers when the API breaks at 2 a.m.? If the answer is “us,” hire specialists. If the answer should be “the vendor,” scope a team.
One architecture conversation decides whether this API keeps your roadmap fast or taxes every release after it — and it costs an hour.
Fintech
Fintech
Fintech
