Deployment Models
SaaS + On-Premise
01
Deployment Architecture
LedgerFlow supports both SaaS (cloud-hosted) and on-premise deployments from a single codebase. Multi-tenancy is achieved via row-level security or schema isolation for large tenants.
Deployment Models
| Model | Description | Tenancy | Scaling |
|---|---|---|---|
| SaaS (Default) | Cloud-hosted, fully managed | Shared database with row-level isolation | Horizontal (stateless API, read replicas) |
| Dedicated SaaS | Large tenant on separate infra | Dedicated database schema or instance | Vertical + horizontal scaling |
| On-Premise | Self-hosted, customer-managed | Single-tenant or private multi-tenant | Customer-controlled |
SaaS Infrastructure
- Container Orchestration: Kubernetes (EKS, GKE, or AKS)
- API Servers: Auto-scaling pod replicas, load-balanced via nginx/Envoy ingress
- Worker Tier: Async job processing for reports, imports, filings; separate scaling from API
- Database: PostgreSQL managed service (RDS, Cloud SQL, Azure DB) with read replicas
- Cache Layer: Redis for session storage, rate limiting, and query caching
- Message Queue: RabbitMQ or AWS SQS for async task distribution
- Object Storage: S3 or GCS for file attachments, exports, backups
- CDN: CloudFront / Cloudflare for static assets and API responses
Kubernetes Deployment
- Namespace per tenant: Logical isolation, dedicated resources for large tenants
- Pod Autoscaling: HPA based on CPU (80%), memory (70%), or custom metrics
- Node Autoscaling: Cluster autoscaler to add/remove nodes based on pod demand
- Rolling updates: Zero-downtime deployments with health checks and canary releases
- Secrets management: HashiCorp Vault or cloud-native secret stores (AWS Secrets Manager, Azure Keyvault)
- Persistent Volumes: For temporary worker storage; ephemeral for replicated state
On-Premise Deployment
- Docker Compose or Helm Charts for single-server deployments
- Kubernetes option for multi-server clusters
- PostgreSQL in local Docker container or external managed database
- Email integration via customer's SMTP server or cloud email service
- File storage on local volumes or NFS
- Licensing & activation via license key or air-gapped mode
02
Database & Data
Database Technology: PostgreSQL
- Version: PostgreSQL 13+ (LTS)
- Multi-tenancy: Row-level security (RLS) policies per tenant; shared schema
- Large tenants: Dedicated schema or database partition with dynamic routing
- Replication: Streaming replication to read replicas; cascade replication for HA
- Backups: WAL-G for incremental backups, automated daily + hourly snapshots
- PITR: Point-in-time restore capability via WAL archival (minimum 30 days)
- Constraints: CHECK constraints to enforce debit=credit invariant per voucher
- Indexes: Composite indexes on (tenant_id, company_id, date) for performance
Data Model Sizing
| Entity | Typical Growth | Index Strategy |
|---|---|---|
| Vouchers (annual) | 10K-50K per small company | Index on date, type, status, company_id |
| Ledger Entries (annual) | 50K-200K per company | Composite (company_id, ledger_id, date) |
| Stock Movements | 5K-20K per year | Index on item_id, godown_id, date |
| Audit Log (annual) | 200K-500K events | Partition by month on created_at |
Query Performance
Standard reports (P&L, Balance Sheet) for a year of data must complete in under 3 seconds. Use materialized views for common aggregations; invalidate nightly or on key posting events.
Backup & Disaster Recovery
- Automated backups: Full daily snapshot + hourly incremental (WAL)
- Retention: 30-day rolling window for PITR; 7-year archive for compliance
- Testing: Weekly restore test to verify backup integrity
- Geographic redundancy: Backups replicated to separate region (India → EU or UAE)
- RTO (Recovery Time Objective): 4 hours for full database restore
- RPO (Recovery Point Objective): 1 hour (max data loss)
03
Scalability & Performance
Horizontal Scalability
| Component | Scaling Method | Limit/Notes |
|---|---|---|
| API Servers | Kubernetes HPA (CPU/memory-based) | Min 3, max 100 replicas per phase |
| Worker Nodes | Separate worker pods, job queue-based | Scale independently of API |
| Database Read Replicas | Stream replication; manual promotion | Up to 10 replicas; route reports to read replicas |
| Cache (Redis) | Cluster mode or sentinel HA | Separate cache per large tenant if needed |
| Object Storage | S3/GCS auto-scaling | Unlimited; object lifecycle policies for archives |
Performance Targets
- Voucher Save: <300 ms (median) / <1 s (p99)
- Report Generation: <3 s for Trial Balance, P&L, Balance Sheet (1 year of data)
- API Response Time: <200 ms (p50) / <500 ms (p99) for typical queries
- Login Time: <2 s (including MFA)
- Concurrent Users per Tenant: Support 50 concurrent users without degradation
- Data Import Speed: 1000 transactions per second (CSV import)
Load Testing Requirements
- Baseline: 1000 concurrent users, 100 transactions/second
- Spike: 5000 concurrent users (month-end close, filing deadline)
- Sustained: 24-hour load test at 80% peak capacity
- Failover: 1 database failure recovery under load; 1 API node failure
- Metrics to track: Response time percentiles (p50, p95, p99), error rate, CPU, memory, disk I/O
04
Security & Compliance
Encryption
- In Transit: TLS 1.2+ (minimum) on all external endpoints; TLS 1.3 preferred
- At Rest: AES-256 encryption for sensitive data (vault fields, audit logs); managed keys via AWS KMS / Azure KeyVault
- Key Rotation: Annual rotation with versioning; no downtime rotation
- Database Encryption: Transparent Data Encryption (TDE) at PostgreSQL level
- Backup Encryption: All backups encrypted with separate key material
Authentication & Authorization
- Authentication: OAuth 2.0 / OIDC for user login; API keys for third-party apps
- MFA: TOTP (Google Authenticator, Microsoft Authenticator) mandatory for admins
- Session Management: 30-minute inactivity timeout; 24-hour absolute session limit
- Password Policy: Min 12 characters, complexity rules; no password reuse (10 generations)
- RBAC: Fine-grained permissions per module, action, and data scope (company, department)
- SSO: SAML 2.0 and OIDC for enterprise tenants; directory integration (LDAP, Active Directory)
Compliance Standards
- SOC 2 Type II: Annual audit covering availability, processing integrity, security, and confidentiality
- ISO 27001: Information Security Management certification
- GDPR: Data privacy compliance; right to deletion and data portability
- India Data Protection: Digital Personal Data Protection Act compliance
- UAE Regulations: Data localization requirements; Central Bank directives
- Financial Audit Trail: Immutable audit logs; non-repudiation for critical actions
Vulnerability Management
- Scanning: Automated SAST (SonarQube), DAST (OWASP ZAP), and dependency scanning (Snyk) in CI/CD
- Penetration Testing: Quarterly by third-party; bug bounty program post-launch
- Patch Management: Monthly security updates; critical patches within 48 hours
- Dependencies: Automated alerts for vulnerable packages; max 30 days to patch
Data Residency & Sovereignty
- India: Data must reside in AWS Mumbai or equivalent Tier-1 Indian facility
- UAE: Data must reside within UAE jurisdiction; no international transfer without written consent
- Tenant-scoped: Customers can specify storage region at signup; cross-region transfers prohibited
- Backup: Primary backup in same region; archive copy per retention policy
05
Operational Requirements
Availability & SLA
- Uptime Target: 99.9% (monthly; 43 minutes downtime allowed)
- Maintenance Windows: Rolling updates, no coordinated downtime required
- Incident Response: 30-minute mean time to detect (MTTD); 4-hour mean time to resolve (MTTR) for severity 1
- Communication: Status page (statuspage.io) with real-time incident updates
- Escalation: On-call rotation; SMS/email alerts for ops team
Monitoring & Observability
- Metrics: Prometheus for scraping; 15-second retention for live, 1-year for archive
- Logs: Structured JSON logging; centralized via ELK (Elasticsearch, Logstash, Kibana) or Datadog
- Tracing: Distributed tracing via Jaeger or AWS X-Ray; 100% sampling for errors, 1% for success paths
- Dashboards: Real-time dashboards for API latency, error rates, database connections, cache hit ratio
- Alerts: Alert on P99 latency >500ms, error rate >0.1%, disk usage >80%, replica lag >30s
Capacity Planning
- Growth Forecast: 50% YoY growth in tenant count; 100% growth in transaction volume
- Headroom: Maintain 2x headroom for compute; 3x for storage
- Quarterly Review: Trending analysis; infrastructure upgrades 2 quarters in advance
- Testing: Load test new infrastructure before production promotion
Disaster Recovery
- Region Failover: Automated failover to secondary region for database (RPO 1 hour, RTO 4 hours)
- API Failover: Sub-second failover via load balancer; auto-drain connections
- Testing: Quarterly failover drill; documented runbook for manual recovery
- Communication: Incident timeline and root cause published within 48 hours
06
Integration Points
Email & Communication
- SMTP: Customer's own SMTP server or managed service (SendGrid, AWS SES)
- Templates: Payslips, invoices, reports via Jinja2 templating; customer-customizable
- Compliance: Email delivery with non-repudiation receipt; audit log of all sends
Government Portals & APIs
- India GST Portal: GSTR JSON submission, e-invoicing (Eway bill, IRN), return filing
- UAE Customs: E-commerce declaration, duty mapping APIs
- Banks: NEFT/RTGS file formats (NPCI standardized); future bank feeds via Yodlee
Third-Party Integrations
- E-commerce: Shopify, WooCommerce (order, payment sync)
- CRM: Salesforce, HubSpot (customer data sync)
- HRMS: BambooHR, Workday (attendance, payroll)
- Storage: Google Drive, OneDrive (document storage fallback)
07
Localization & Globalization
Language Support
- Primary: English (en-US, en-IN, en-AE)
- Secondary: Hindi (hi-IN), Arabic (ar-AE, ar-SA)
- Infrastructure: i18n (i18next or similar) for UI strings; database for configurable terms (ledger group names)
- RTL Support: Full CSS RTL layout for Arabic; bidirectional text rendering
Number & Date Formatting
- Numbers: Locale-aware decimal separator (. for en, , for hi) and thousands grouping
- Dates: DD-MM-YYYY for India, DD/MM/YYYY for UAE, MM-DD-YYYY fallback for others
- Currency: Multiple currency symbols (₹ ₨ $ €); no currency conversion (customer-configured)
- Fiscal Year: Configurable FY start (04-01 for India, 01-01 for calendar-year companies, 07-01 for UAE entities)
Tax Localization
- India: GST 5/12/18/28%, HSN codes, GSTR returns, TDS sections, PF/ESI
- UAE: VAT 5%, specific registration thresholds, e-invoicing formats, payroll (WPS)
- Extensibility: Configuration-driven tax rules; no code changes for new tax rates