When technology executives evaluate transitioning from commercial e-signature SaaS to a self-hosted architecture, financial controllers immediately ask the practical question: "How much will this actually cost to run on our cloud servers?"
Vendors selling expensive per-envelope SaaS subscriptions often attempt to dissuade self-hosting by claiming that private cloud infrastructure is prohibitively complex and expensive to maintain. In reality, modern containerized signing software is remarkably lightweight. A well-architected self-hosted signing platform running on AWS, Azure, or private virtual servers requires only a fraction of the budget consumed by commercial SaaS subscription invoices.
To build an accurate, audit-ready infrastructure budget for your finance team, you must model the specific cloud components required across realistic operational volume levels.
The Cloud Infrastructure Bill of Materials
A resilient, production-ready e-signature platform comprises five primary cloud infrastructure components:
| Cloud Component | Recommended Specification | Primary Workload Handled |
|---|---|---|
| Application Compute | 2x t4g.medium (AWS ECS / Docker) | Handling web signing views, REST API endpoints, and PDF compilation. |
| Relational Database | AWS RDS PostgreSQL db.t4g.small (Multi-AZ) | Document metadata, audit event logs, user roles, and account records. |
| Object Storage | AWS S3 Standard (with lifecycle to Glacier) | Immutable storage for signed PDFs, templates, and cryptographic certificates. |
| Ingress / Networking | AWS Application Load Balancer (ALB) | SSL/TLS termination, health checks, and cross-AZ traffic routing. |
| Operational Monitoring | AWS CloudWatch & S3 backup snapshots | Container metric logging, error alerting, and automated daily backups. |
Three-Tier Cloud Infrastructure Cost Model
Infrastructure expenses scale with document volume. The following model details realistic monthly and annual cloud costs based on standard on-demand US/EU AWS pricing:
| Infrastructure Component | Low Tier (10,000 docs/yr) Single-AZ / Dev-Ready |
Mid Tier (50,000 docs/yr) Multi-AZ High Availability |
High Tier (250,000 docs/yr) Enterprise Auto-Scaling |
|---|---|---|---|
| Application Compute | $30 / month (1x t4g.medium) | $60 / month (2x t4g.medium) | $120 / month (4x t4g.medium auto-scale) |
| Managed Database | $35 / month (RDS db.t4g.micro) | $68 / month (RDS db.t4g.small Multi-AZ) | $136 / month (RDS db.t4g.medium Multi-AZ) |
| S3 Document Storage | $2 / month (~50GB storage) | $8 / month (~250GB storage) | $30 / month (~1.2TB storage) |
| Load Balancer & Egress | $20 / month | $25 / month | $35 / month |
| Backups & CloudWatch | $5 / month | $10 / month | $25 / month |
| Total Monthly Cloud Cost | $92 / month | $171 / month | $346 / month |
| Total Annual Cloud Cost | $1,104 / year | $2,052 / year | $4,152 / year |
Contrasting Cloud Hosting Against SaaS Invoices
Comparing these cloud infrastructure figures against commercial SaaS invoices demonstrates the overwhelming financial leverage of self-hosting:
The 50,000 Document Comparison: At fifty thousand documents annually, an enterprise paying a standard negotiated SaaS rate of $2.20 per envelope incurs $110,000 in annual software fees. Hosting that exact same workload on a robust, multi-AZ self-hosted Undersign deployment incurs approximately $2,052 in annual cloud infrastructure costs. The infrastructure overhead represents less than two percent of the SaaS invoice.
The 250,000 Document Comparison: At a quarter-million documents, commercial SaaS invoices easily surpass $400,000 annually. On private cloud infrastructure, scaling to handle that volume requires approximately $4,152 in annual AWS compute, database, and storage resources, saving over $390,000 in recurring operating expenses every single year.
Three Operational Rules of Thumb for Cloud Sizing
When configuring your cloud resources, keep these sizing principles in mind:
- Average PDF Storage Footprint: An executed contract with embedded vector signatures and an audit certificate averages 500KB to 1.5MB in size. One hundred thousand completed documents consume approximately 100GB of storage. S3 Standard storage costs just $0.023 per GB per month ($2.30/mo for 100k contracts).
- Compute vs Database Balance: The primary compute spikes occur during PDF generation, digital hashing, and rasterization. Scale container CPU before scaling database compute. A modest database handles millions of metadata rows without breaking a sweat.
- Leverage S3 Lifecycle Rules: Configure automated lifecycle policies to transition documents older than ninety days from S3 Standard to S3 Infrequent Access or S3 Glacier Flexible Retrieval, reducing long-term archival costs by up to eighty percent.
Budgeting Summary
Running a self-hosted e-signature platform on modern cloud infrastructure is neither complicated nor expensive. For mid-sized to enterprise organizations, total hosting costs range from $1,000 to $4,500 annually. When paired with a one-time software license from Undersign, self-hosting represents one of the most profitable capital optimizations in enterprise IT.