# Custom API Integration Services — Connect Your ERP, CRM, Legacy Systems, and SaaS Tools Without Rip-and-Replace Custom API integration is the bespoke work of connecting your business systems — ERP, CRM, e-commerce, warehouse management, accounting, marketing automation, and legacy in-house applications — so they share data automatically instead of through spreadsheets, copy-paste, and tribal knowledge. FreedomDev has built more than 200 production API integrations for mid-market companies in the last 18 years. We are not a unified API platform (Merge, Workato, Nango) — those products are right for connecting to common SaaS endpoints. We are the team you hire when the integration involves a 1996-era ERP that has no API, a custom application written in-house by someone who left in 2014, or an SAP S/4HANA flow that does not fit any product's predefined connector. ## Custom API Integration Services — Connect Your ERP, CRM, Legacy Systems, and SaaS Tools Without Rip-and-Replace Custom API integration is the bespoke work of connecting your business systems — ERP, CRM, e-commerce, warehouse management, accounting, marketing automation, and legacy in-house applications — so they share data automatically instead of through spreadsheets, copy-paste, and tribal knowledge. FreedomDev has built more than 200 production API integrations for mid-market companies in the last 18 years. We are not a unified API platform (Merge, Workato, Nango) — those products are right for connecting to common SaaS endpoints. We are the team you hire when the integration involves a 1996-era ERP that has no API, a custom application written in-house by someone who left in 2014, or an SAP S/4HANA flow that does not fit any product's predefined connector. --- ## Our Process 1. **Discovery call (30-60 min)** — describe the integration scope, the source and destination systems, the volume and frequency 2. **Discovery week** — paid scope; we document both systems, propose the integration pattern, write the spec 3. **Architecture proposal** — flat-rate quote for the build; deliverables and milestones 4. **Build phase** — typically 4-12 weeks; weekly demos to your team; we use whatever stack your engineering team prefers 5. **Lower-environment validation** — staging integration; data correctness checks 6. **Production cutover** — shadow mode → active mode; documented rollback plan 7. **Stabilization** — 2-4 weeks watching production, tuning, transferring knowledge 8. **Handoff** — code in your repository, runbook in your wiki, on-call procedures documented We do not retain client integrations as black-box dependencies. Code lives in your repository. Your team can read it, modify it, and run it without us. --- ## Frequently Asked Questions ### What are custom API integrations? (PAA capture) Custom API integrations are bespoke connections built specifically for your data flows between two or more business systems. Unlike generic connectors (Zapier, Make, Workato) that work for common SaaS pairs, custom integrations handle the specific transformations, business rules, error-handling, and authentication required for your systems and your processes. Custom is the right choice when at least one system is legacy or custom-built, when data transformation is non-trivial, when volume exceeds platform tier limits, or when long-term ownership of the integration code matters. ### What are API integration services? (PAA capture) API integration services are professional services firms that build integrations between business systems on your behalf. The scope includes discovery (understanding what data needs to flow where), architecture design (choosing the integration pattern), build (writing and deploying the integration code), validation (testing in non-production environments), production deployment, and stabilization. Most engagements run 6-16 weeks per integration depending on complexity. ### Should I use Merge.dev, Workato, Zapier, or a custom build? Match the tool to the scope. **Zapier and Make**: best for simple workflows triggered by common SaaS events; low cost, fast setup, limited flexibility. **Workato and Tray**: enterprise iPaaS for organizations with many integrations and budget for $50-200k/year platforms. **Merge.dev and Nango**: unified API platforms for products that need to integrate with many SaaS providers in their customer's stack (typical for B2B SaaS vendors). **Custom**: when legacy systems are involved, when data transformation is complex, when you want code-level ownership, or when 3-5 year TCO matters more than year-1 setup speed. ### How long does a custom API integration take? Single integration with modern APIs on both sides: 4-8 weeks. Single integration with one legacy or custom system: 8-12 weeks. Multi-integration project: 12-24 weeks depending on count and complexity. Discovery alone is 1-2 weeks; the build phase is the largest, and stabilization is 2-4 weeks post-go-live. We give flat-rate quotes after discovery, not before — quoting blind is how integration projects go 200% over budget. ### Can we use FreedomDev for one integration now and decide later about more? Yes. About 60% of our integration clients start with one integration and expand to a 5-10 integration portfolio over 2-3 years. Each integration is scoped independently. There is no platform license or retainer requirement; integrations live in your codebase and your team can maintain them between engagements. ### What is your 99.8% reliability claim based on? Production telemetry across the integrations we have built and currently support. The 99.8% measures successful end-to-end transaction completion (source event → integration service → destination acknowledgment) over rolling 30-day windows. The 0.2% accounts for transient failures (network timeouts, brief downstream outages) and permanent failures (validation rejections that route to DLQ for human review). We publish reliability targets per engagement and report against them monthly for retainer clients. ### What is the four types of REST APIs? (PAA capture — answer briefly to capture this PAA) The question is loosely phrased; there is no standard "four types" of REST API. The most common framing of "API types" buckets APIs as public (open to anyone with an API key), partner (open to vetted partner organizations), private/internal (within your own organization), and composite (single endpoint that orchestrates multiple downstream calls). For implementation, the four HTTP methods most commonly used are GET (read), POST (create), PUT/PATCH (update), and DELETE (delete) — sometimes informally called "the four REST verbs." --- **Canonical URL**: https://freedomdev.com/solutions/api-integration _Last updated: 2026-05-12_