01 · Legacy API wrapping
A clean REST or GraphQL layer over old systems.
Expose existing mainframe, ERP, or monolith functionality through a clean REST or GraphQL layer without touching the source system.
Legacy integration · API bridges · Data sync
Connect systems that were never meant to talk.
When a new platform needs to work alongside a legacy system that cannot be replaced yet, bridge engineering fills the gap. We build the adapters, translators, and sync layers that let old and new coexist without a risky big-bang migration.
Capabilities
Every layer between a legacy system and a modern one.
Bridge engineering is not a single technique. It is a set of patterns applied where they fit: wrappers, translators, queues, incremental routing, and full ETL when needed.
02 · Data translation layers
Map between incompatible data models.
Map between incompatible data models, handle format differences, and normalize records as they cross system boundaries.
03 · Event-driven sync
No polling, no tight coupling.
Use message queues or webhooks to keep two systems in sync without tight coupling or polling overhead.
04 · Strangler fig migrations
One feature at a time, instant rollback.
Incrementally route traffic from old to new, one feature at a time, with instant rollback on any issue.
05 · ETL pipelines
Scheduled or real-time with full audit logging.
Extract, transform, and load data between systems on a schedule or in real time with full audit logging.
06 · Integration testing
End-to-end tests across both sides of the bridge.
End-to-end test suites that verify both sides of a bridge behave correctly as either system changes.
How we work
Four phases. Same team across all four.
The phases that apply to every engagement, not just bridge engineering. The team that scopes does the building, and the operating.
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Phase 01 · 2–4 weeks
Discovery and scope.
Stakeholder interviews, technical review of existing systems, risk register, written scope with milestones and exit criteria.
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Phase 02 · 3–12 months
Build and iterate.
Two-week sprints with working demos. Senior leads on every sprint review. Code reviewed, accessibility checked.
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Phase 03 · 2–6 weeks
Cutover and stabilization.
Parallel run with rollback path. On-call coverage during the launch window. Stabilization continues until incident rate trends to zero.
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Phase 04 · ongoing
Operate and evolve.
Multi-year retainer with the same team that built the product. Monthly check-ins, quarterly business reviews.
Read the full engagement model on the How We Work page.
Industries we serve
Bridge engineering across 15 verticals.
Six core verticals where OST has the deepest engagement experience. Plus nine adjacent industries served on selective engagements.
01
Education
K-12 charter networks, higher education, public sector portals.
02
Nonprofit & Civic
Donor-cycle nonprofits, advocacy organizations, civic platforms.
03
Healthcare & Wellness
HIPAA-aware platforms, medical directories, telemedicine adjacency.
04
Real Estate Technology
Multi-tenant SaaS, brokerage tools, self-storage operators.
05
E-commerce & Marketplaces
OpenCart specialists, custom commerce, $10B+ in transactions processed.
06
Manufacturing & B2B
Industrial platforms, B2B safety-tech, embedded engineering teams.
Also serves on selective engagements
Frequently asked questions
Common questions on bridge engineering engagements.
When does bridge engineering make more sense than a full migration?
When the legacy system cannot be decommissioned on the timeline a new platform needs. When migration risk is too high for a big-bang cutover. When two systems will genuinely coexist long-term. We help you decide which approach fits your situation in discovery.
Will the bridge slow down the new system?
A well-designed bridge adds minimal latency. We scope latency budgets during discovery and design accordingly. Event-driven patterns (queues, webhooks) decouple systems so one side does not block the other.
What does a bridge engineering engagement cost?
Single-point API wrapper: $20K to $50K. Full bidirectional sync with translation layer: $60K to $150K. ETL pipeline with monitoring and audit trail: similar range. Use our cost calculator for a bracket.
What if the legacy system has no API?
Common situation. We assess what interfaces exist: database access, file exports, screen-scraping as a last resort. Discovery surfaces which approach is viable and what the trade-offs are before we commit to a design.
How do you handle data consistency between two live systems?
We design for eventual consistency by default and document the consistency window. Where stronger guarantees are needed, we use two-phase commit patterns or designate a single system of record for each data type.
Ready to connect your systems?
Pick a path forward.
Multiple ways to start: schedule a discovery call, run our cost calculator for a budget bracket, or use the contact form for a written response.