How to Build an LRN API
A technical guide to building your own LRN lookup system — including the architecture, NPAC data access requirements, and an honest assessment of build vs. buy.
Architecture Overview
A production LRN API requires these components:
- NPAC Data Source — Authorized feed of porting events and current LRN data
- Primary Database — MySQL or PostgreSQL with 400M+ NANP records, ~20 GB
- Change Replication — Continuous ingestion of NPAC porting events
- Redis Cache Layer — L1 in-memory cache for hot number ranges
- REST API Layer — HTTPS endpoint with authentication and rate limiting
- Monitoring — Latency, availability, and data freshness tracking
Database Schema
The core LRN table needs:
CREATE TABLE lrn_numbers (
number VARCHAR(10) NOT NULL,
lrn VARCHAR(10) NOT NULL,
ocn VARCHAR(10),
spid VARCHAR(10),
rate_center VARCHAR(20),
lata VARCHAR(10),
line_type ENUM('landline','wireless','voip'),
ported BOOLEAN DEFAULT FALSE,
updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (number),
INDEX idx_lrn (lrn),
INDEX idx_ocn (ocn)
) ENGINE=InnoDB;NPAC Access Requirements
To receive authoritative NPAC data, you need to become an authorized NPAC service provider. This involves:
- FCC carrier authorization (Form 499-A filing)
- iconectiv NPAC participation agreement
- Annual participation fees ($50K–$200K depending on tier)
- Technical integration with NPAC's specific data feed formats
Redis Caching Strategy
For production throughput, you'll need a Redis cluster caching hot number ranges. Set TTLs of 30–60 seconds for numbers in active porting periods and longer TTLs (10+ minutes) for stable ranges. Cache hit rates of 60–70% are typical for carrier call traffic patterns.
The Build vs. Buy Reality
Here's what building your own LRN API actually costs:
| Cost Item | Estimate | Complexity |
|---|---|---|
| NPAC Authorization & Fees | $50K–$200K/yr | High |
| Database Infrastructure (MySQL/Redis) | $2K–$10K/mo | Medium |
| Engineering Build Time | 3–12 months | High |
| Ongoing Maintenance | 0.5–1 FTE | Medium |
| Uptime Monitoring & Ops | $1K–$5K/mo | Medium |
At SIPSmart pricing, you would need >500 million lookups per month before in-house becomes cost-competitive — and that's before accounting for engineering time and uptime risk.
Skip the Build. Use Ours.
We've built the NPAC-direct infrastructure already. Sub-10ms P99, 400M+ records, 99.99% SLA. Start with 1,000 free lookups — no engineering required.
Skip the Build — Full API Reference
See exactly what the SIPSmart API returns: endpoint schema, error codes, latency targets, code examples.
- Build estimates range from 3–12 months for a production-quality LRN API with NPAC connectivity, database replication, caching, and monitoring. Ongoing maintenance (NPAC protocol updates, database scaling, uptime) adds significant recurring cost. Most teams find it cheaper to use a managed provider.
- Direct NPAC access requires FCC authorization, participation fees, and compliance with iconectiv's technical specifications. Most carriers access NPAC through authorized service providers who redistribute data via API or database replication.
- For low volumes (<100K/month), a managed API like SIPSmart is almost always cheaper than building and maintaining your own. For very high volumes (100M+/month), some carriers evaluate building in-house, but the NPAC access costs alone often make managed providers competitive.
We Already Built It. Use Ours.
NPAC-direct LRN API. No NPAC fees, no database management, no ops overhead.
1,000 free lookups included • No credit card required • Instant provisioning