Building a Multi-System Astrology Platform: Architecture for Vedic, Western, Tarot, and Beyond

Most astrology APIs cover one system. You get Western tropical astrology, or you get Vedic Jyotish, or you get tarot. Rarely do you get all of them, and almost never through a single API key with a unified developer experience.

The reason is architectural complexity. Western and Vedic astrology use fundamentally different zodiac systems. Tarot and I-Ching have completely different data models from astrology. Numerology derives meaning from letter-number mappings that have no astronomical basis at all. Building a platform that handles all of these requires more than bolting separate codebases together. It requires a deliberate architecture that normalizes where possible, isolates where necessary, and presents a coherent interface to the developer.

This article walks through the engineering decisions behind building a multi-system insight platform, from data modeling to API design to the challenges that only surface when you try to make fundamentally different systems coexist.

The Problem: Six Systems, Six Data Models

Consider what a multi-system platform needs to support:

Western (Tropical) Astrology

• 12 zodiac signs tied to the spring equinox (tropical zodiac)
• 10 planets (Sun through Pluto) plus lunar nodes and asteroids
• 15+ house systems dividing the ecliptic into 12 segments
• Aspects (angular relationships between planets)
• Transits (current planet positions relative to natal chart)
• Synastry (chart comparison for compatibility)
• Progressions (symbolic time-advancing of the natal chart)

Vedic (Sidereal) Astrology

• 12 zodiac signs shifted ~24 degrees from tropical (sidereal zodiac, multiple ayanamsa options)
• 9 grahas (traditional planets, excluding Uranus/Neptune/Pluto, adding Rahu/Ketu)
• 27 nakshatras (lunar mansions spanning 13 degrees 20 minutes each)
• 16+ divisional charts (D-1 Rashi through D-60 Shashtiamsha)
• Vimshottari Dasha system (planetary periods spanning decades)
• 300+ yogas (planetary combinations with specific meanings)
• Ashtakavarga (point-based strength assessment)
• Panchang (daily tithi, karana, yoga, nakshatra)
• KP (Krishnamurti Paddhati) system with 249 sub-lord divisions

Tarot

• 78 cards (22 Major Arcana + 56 Minor Arcana across 4 suits)
• Upright and reversed meanings per card
• Multiple spread layouts (Celtic Cross, 3-card, relationship, career)
• Positional meaning (same card means different things in different spread positions)
• Seeded randomness for reproducible readings

Numerology

• Letter-to-number mapping systems (Pythagorean, Chaldean)
• Core numbers: Life Path, Destiny, Soul Urge, Personality, Maturity
• Master numbers (11, 22, 33) with special handling
• Karmic debt numbers (13, 14, 16, 19)
• Personal year/month/day cycles
• Name-based and date-based calculations

Dream Interpretation

• Symbol-based lookup (2,000+ dream symbols)
• Category grouping (animals, water, falling, people, objects)
• Psychological and spiritual interpretation layers
• Context-dependent meanings

I-Ching

• 64 hexagrams composed of 8 trigrams
• Line-by-line readings (6 lines per hexagram, each with individual meaning)
• Changing lines that transform one hexagram into another
• Three-coin casting method with probabilistic outcomes
• Traditional judgments plus modern interpretive text

These six systems share almost no data structures. A planet position (floating point longitude) has nothing in common with a tarot card (symbolic archetype with positional meaning). A nakshatra (lunar mansion) has no equivalent in numerology. An I-Ching hexagram has no parallel in Western astrology.

Architecture Decision 1: Modular Monolith, Not Microservices

The first architectural choice is how to organize code. Three options:

Monolithic single codebase: Everything in one application. Simple deployment, but domains bleed into each other. A change to the Vedic dasha calculator risks breaking tarot card shuffling.

Microservices: Each system as a separate service. Maximum isolation, but massive operational overhead for a small team. Six services means six deployments, six monitoring configs, six sets of logs, and network latency between services.

Modular monolith: Each system as an independent module (package) within a single deployable application. Isolated code boundaries, shared infrastructure (auth, rate limiting, error handling), zero network latency between modules, single deployment.

The modular monolith wins for multi-system platforms. Each domain gets its own package with its own routes, schemas, and calculation logic. A shared application shell provides middleware (API key validation, rate limiting, usage tracking) that applies uniformly across all domains.

src/
  shared/            # Auth, rate limiting, usage tracking, error handling
  api/               # Route mounting and OpenAPI generation

domains/
  western-astrology/   # Western tropical astrology
  vedic-astrology/     # Vedic sidereal astrology (Jyotish + KP)
  tarot/               # Tarot card readings
  numerology/          # Pythagorean numerology
  dreams/              # Dream interpretation
  iching/              # I-Ching oracle

Each domain module exports its routes and metadata. The main application mounts them at their respective URL paths and applies shared middleware. Adding a new domain (say, palmistry or feng shui) means creating a new module and registering it, with zero changes to existing domains.

Why This Matters for Developers

From the API consumer perspective, this architecture means:

• One API key for all domains. No separate subscriptions per system.
• One authentication flow. The API key works the same for astrology, tarot, and numerology.
• One rate limit. Your monthly request quota applies across all endpoints.
• One OpenAPI spec. All endpoints documented in a single spec, plus per-domain specs if you want only one system.
• One MCP server per domain. AI agents discover tools for the specific system they need.

Architecture Decision 2: Normalize the Shared, Isolate the Unique

The temptation with a multi-system platform is to create a universal data model. A "CelestialBody" type that covers planets, tarot cards, hexagram lines, and numerological numbers. This is a trap. These concepts are fundamentally different. Forcing them into a shared model creates leaky abstractions that make every domain harder to work with.

What to Normalize

Request patterns: Every domain needs a way to receive input parameters and return structured output. Normalize the request/response contract:

• All endpoints accept JSON request bodies
• All endpoints return JSON responses
• All errors follow the same structure: { "error": { "code": "...", "message": "..." } }
• All endpoints are documented in OpenAPI with descriptions on every field

Authentication and billing: One API key, one rate limiter, one usage counter. The billing system does not need to know whether a request calculates a birth chart or draws a tarot card. A request is a request.

Response metadata: Standard rate limit headers on every response regardless of domain:

X-RateLimit-Limit: 5000
X-RateLimit-Remaining: 4832
X-RateLimit-Used: 168

What to Isolate

Domain logic: Tarot card shuffling has nothing to do with ephemeris calculations. Dasha period computation has nothing to do with dream symbol lookup. Each domain implements its own calculation engine with zero dependencies on other domains.

Data models: A planet has longitude, latitude, speed, sign, and house. A tarot card has name, arcana, suit, upright meaning, and reversed meaning. A hexagram has six lines, upper trigram, lower trigram, judgment, and image. These are distinct types with distinct schemas.

Route definitions: Each domain defines its own routes with its own request/response schemas. There is no shared "calculate" endpoint that dispatches to different systems. Instead:

POST /api/v2/astrology/birth-chart          # Western natal chart
POST /api/v2/vedic-astrology/birth-chart     # Vedic natal chart
POST /api/v2/tarot/reading                   # Tarot card reading
POST /api/v2/numerology/life-path            # Life path number
POST /api/v2/dreams/interpret                # Dream symbol lookup
POST /api/v2/iching/reading                  # I-Ching hexagram cast

Each path segment clearly identifies the domain. An AI agent or developer immediately knows which system they are working with.

Architecture Decision 3: The Astrology Divergence Problem

Western and Vedic astrology deserve special attention because they appear similar but diverge in fundamental ways.

What They Share

Both systems compute planetary positions from the same astronomical data. The Sun is at a specific point in the sky regardless of whether you interpret it through a tropical or sidereal lens. Both use the same ephemeris engine. Both need birth date, time, and geographic coordinates as input.

Where They Diverge

Concept	Western (Tropical)	Vedic (Sidereal)
Zodiac reference	Spring equinox (0 Aries)	Fixed stars (shifted ~24 degrees)
Planets used	Sun through Pluto + asteroids	Sun through Saturn + Rahu/Ketu
Outer planets	Core to the system	Not traditionally used
House systems	Placidus most popular	Whole Sign most common
Subdivision	Degrees, decanates	Nakshatras, padas, sub-lords
Timing system	Transits, progressions	Vimshottari Dasha periods
Compatibility	Synastry (aspect comparison)	Ashtakoot Gun Milan (point matching)
Chart types	Natal, transit, composite	D-1 through D-60 divisional charts
Dignity system	Essential dignities, detriments	Exaltation, debilitation, own sign
Special combos	Aspect patterns (Grand Trine, T-Square)	300+ named yogas

Architectural Implications

The divergence means Western and Vedic astrology must be separate packages, not configuration options on the same endpoints. A "birth chart" endpoint that takes a zodiac_type: "tropical" | "sidereal" parameter might seem elegant, but it creates problems:

• The response schemas are different (Western returns aspects and decans; Vedic returns nakshatras and yogas)
• The planet lists are different (Western includes Uranus/Neptune/Pluto; Vedic uses Rahu/Ketu)
• The interpretation context is completely different
• AI agents need to know which system they are querying for accurate tool selection

Separate packages with separate endpoints (/astrology/birth-chart vs. /vedic-astrology/birth-chart) make the distinction explicit and keep each domain internally consistent.

Architecture Decision 4: Cross-Domain Opportunities

While each domain is isolated, there are legitimate cross-domain features that a multi-system platform enables:

Combined Readings

A user wants "a complete spiritual profile" that includes their Western birth chart, Vedic chart, numerology profile, and a tarot reading. This is an application-layer orchestration problem, not an API-layer merging problem. The API provides individual domain endpoints. The consuming application (or AI agent) calls multiple endpoints and synthesizes the results.

This is the correct separation of concerns. The API provides data. The application (or AI) provides synthesis. Merging them at the API level creates rigid, opinionated endpoints that limit how developers can use the data.

Shared Temporal Context

Several domains share the concept of "what is happening right now." Current planetary transits (Western), today panchang (Vedic), personal year number (numerology), and daily hexagram (I-Ching) all answer some form of "what does today mean?" A multi-system platform can offer these as individual endpoints that applications combine into daily insight features.

User Profile Enrichment

When an application has a user's birth date and birth location, it can enrich the user profile across domains simultaneously:

• Compute natal chart (Western + Vedic)
• Calculate life path number and destiny number
• Determine personal year cycle
• Set up transit alerts for current planetary movements
• Generate ongoing dasha period predictions

A single API key unlocks all of these. A single user input (birth data) feeds multiple systems. This is the core advantage of a multi-system platform over stitching together separate single-domain APIs.

The Normalization Challenges Nobody Talks About

Zodiac Sign Naming

Western astrology uses "Aries, Taurus, Gemini..." Vedic astrology uses both the same English names and Sanskrit equivalents (Mesha, Vrishabha, Mithuna...). Your API needs to decide: return English names everywhere for consistency, or return tradition-appropriate names per system?

The pragmatic answer: English names as the primary field with optional localized names. "sign": "Aries" in both systems, with Vedic responses adding "sign_sanskrit": "Mesha" for applications that want traditional terminology. This lets developers parse sign names consistently across domains while preserving cultural accuracy.

Coordinate Precision

Astrology calculations use decimal degrees. But different consumers need different precision levels:

• Casual horoscope apps: whole degrees are sufficient
• Professional astrologers: degrees and minutes (2 decimal places)
• Research applications: arc seconds (4+ decimal places)
• Astronomical verification: sub-arc-second (6+ decimal places)

Standardize on maximum precision (4-6 decimal places) and let consuming applications round as needed. Never round at the API level, since information lost in the API response cannot be recovered.

Date and Time Handling

This is arguably the hardest normalization problem. Different domains handle time differently:

• Western astrology: Birth time in local timezone, converted to UTC for calculation
• Vedic astrology: Same, but panchang calculations need local apparent time (based on actual sun position, not timezone)
• Numerology: Only birth date (no time), calculated from local date
• Tarot: No time component, but seeded readings need a reproducible seed
• I-Ching: Optional time for traditional hour-based casting

The input contract must be flexible enough to handle "just a date," "date + time," and "date + time + timezone offset" without requiring unused parameters. Optional fields with sensible defaults solve this.

For Developers: Using a Multi-System Platform

If the architecture above sounds like more than you want to build yourself, RoxyAPI provides exactly this: six domains under one API key.

• Western Astrology: Natal charts, planetary positions, transits, synastry, progressions, moon phases, and zodiac horoscopes
• Vedic Astrology: Birth charts, nakshatras, Vimshottari Dasha, 300+ yogas, Ashtakoot compatibility, divisional charts, panchang, and KP system
• Tarot: 78-card Rider-Waite-Smith deck with spreads, reversals, and positional meanings
• Numerology: Life path, destiny, soul urge, personal year cycles, compatibility, and karmic analysis
• Dreams: 2,000+ dream symbols with psychological interpretations
• I-Ching: 64 hexagrams with three-coin casting and line-by-line readings

All 85+ endpoints share one API key, one rate limit, one set of documentation, and one MCP integration for AI agents. View pricing to get started.

# Western birth chart
curl -X POST "https://roxyapi.com/api/v2/astrology/birth-chart" \
  -H "X-API-Key: YOUR_KEY" \
  -d '{"date":"1990-06-15","time":"14:30","latitude":40.71,"longitude":-74.01}'

# Vedic birth chart (same birth data, different system)
curl -X POST "https://roxyapi.com/api/v2/vedic-astrology/birth-chart" \
  -H "X-API-Key: YOUR_KEY" \
  -d '{"date":"1990-06-15","time":"14:30","latitude":40.71,"longitude":-74.01}'

# Numerology life path (same person, different domain)
curl -X POST "https://roxyapi.com/api/v2/numerology/life-path" \
  -H "X-API-Key: YOUR_KEY" \
  -d '{"date":"1990-06-15"}'

Three different systems, one API key, consistent authentication, consistent error handling.

Conclusion

Building a multi-system astrology and divination platform is primarily an architecture problem, not a calculation problem. The individual calculations (ephemeris positions, card shuffling, number reduction) are well-understood. The hard part is designing a system where six fundamentally different domains coexist with isolated logic, shared infrastructure, and a coherent developer experience.

The modular monolith pattern, with shared middleware and isolated domain packages, strikes the right balance between isolation and operational simplicity. Normalizing the shared layer (auth, billing, error formats, rate limiting) while isolating domain-specific logic (schemas, calculations, route definitions) prevents both leaky abstractions and unnecessary duplication.

Key takeaways:

• Six divination/insight systems have fundamentally different data models; forcing them into a universal schema creates leaky abstractions
• Modular monolith architecture provides domain isolation with zero network latency and single deployment
• Normalize the shared infrastructure (auth, rate limits, error handling, OpenAPI) and isolate domain logic
• Western and Vedic astrology must be separate packages, not configuration flags, because response schemas diverge significantly
• Cross-domain features belong in the application layer, not the API layer, since the API provides data while the application provides synthesis
• Date/time handling is the hardest normalization problem due to different time requirements per domain

Explore how a multi-system platform works in practice: RoxyAPI unifies six domains under one key. Browse the complete API documentation or check pricing.

Frequently Asked Questions

Q: Why not build one giant API endpoint that handles all astrology systems with a parameter? A: Because the response schemas are fundamentally different. A Western birth chart returns aspects, decanates, and tropical positions. A Vedic birth chart returns nakshatras, yogas, and sidereal positions. Merging them into one endpoint creates a response that is either a confusing union type or a bloated superset with mostly-null fields. Separate endpoints per system keep each response clean and predictable.

Q: Can Western and Vedic astrology share the same calculation engine? A: They share the same ephemeris engine (planetary position computation from astronomical data), but diverge in everything built on top: zodiac reference frame, planet selection, house system preferences, subdivision methods, and timing techniques. The shared layer is thin (coordinate calculation), and the divergent layer is thick (astrological interpretation).

Q: How do you handle the zodiac sign difference between Western and Vedic astrology? A: Western (tropical) and Vedic (sidereal) zodiacs are offset by the ayanamsa value (currently about 24 degrees). The same planet can be in Gemini tropically and Taurus sidereally. Each system returns positions in its own zodiac frame. The API makes this explicit through separate endpoints rather than a zodiac toggle, preventing accidental misinterpretation.

Q: What is the advantage of one API key for multiple domains vs. separate APIs? A: Single API key simplifies authentication (one key to manage), billing (one subscription, one invoice), rate limiting (one quota across all domains), and monitoring (one usage dashboard). For developers building apps that span multiple systems (astrology + tarot + numerology), managing one integration is dramatically simpler than managing three separate vendor relationships.

Q: How does a multi-system platform handle domain-specific errors? A: Error structure is normalized (same JSON format, same HTTP status codes, same error code pattern), but error codes are domain-specific. An astrology endpoint might return INVALID_HOUSE_SYSTEM, while a tarot endpoint returns INVALID_SPREAD_TYPE. The consuming application handles errors consistently at the structural level while branching on domain-specific codes when needed.

Q: Is it better to use microservices or a monolith for a multi-domain API? A: For small to mid-size teams, a modular monolith is better. You get code isolation (each domain in its own package) without the operational overhead of multiple services (separate deployments, service mesh, inter-service communication). Microservices make sense when different domains need independent scaling or different team ownership, but this rarely applies until you reach significant scale.

Q: How does AI agent integration work across multiple domains? A: Each domain provides its own MCP (Model Context Protocol) server with tools specific to that system. An AI agent building an astrology chatbot connects to the astrology MCP server. An agent building a spiritual wellness app connects to multiple MCP servers. The agent discovers tools per domain and calls them individually, combining results at the application layer.

Q: Can I use just one domain from a multi-system platform, or do I have to pay for all of them? A: With flat per-request pricing, you only pay for the API calls you make. If you only use Western astrology endpoints, you pay for those requests. The other domains are available but cost nothing until you call them. This gives you the flexibility to expand into new domains without changing your API subscription or integration code.