Kora operator

Kora Node Operator Guide

Run Kora nodes to validate, sign, and sponsor Solana transaction fees for your users.

Docs: https://launch.solana.com/docs/kora/operators Install: cargo install kora-cli Docker: docker pull ghcr.io/solana-foundation/kora:latest Source: https://github.com/solana-foundation/kora

Quick Start

# Install
cargo install kora-cli

# Minimal config files needed: kora.toml + signers.toml

# Validate config
kora --config kora.toml config validate

# Start server
kora --config kora.toml rpc start --signers-config signers.toml

# Initialize payment ATAs (for receiving token payments)
kora --config kora.toml rpc initialize-atas --signers-config signers.toml

CLI Reference

# Global flags
kora --config <path>     # kora.toml location (default: ./kora.toml)
kora --rpc-url <url>     # Solana RPC URL (overrides config, env: RPC_URL)

# Commands
kora config validate                    # Validate kora.toml
kora config validate-with-rpc           # Validate with live RPC calls
kora rpc start --signers-config <path>  # Start RPC server
kora rpc start --no-load-signer         # Start without loading signers (limited functionality)
kora rpc start --port 8080              # Custom port (default: 8080)
kora rpc start --logging-format json    # JSON logging (default: standard)
kora rpc initialize-atas --signers-config <path>  # Initialize payment ATAs

# ATA init options
--fee-payer-key <base58>     # Custom fee payer for ATA creation
--compute-unit-price <num>   # Priority fee
--compute-unit-limit <num>   # Compute budget
--chunk-size <num>           # Batch size for ATA creation

Configuration Overview

Two config files required:

File	Purpose
kora.toml	Server config: validation, auth, pricing, caching, methods, bundles, lighthouse, metrics
signers.toml	Signer pool: keys, types, selection strategy

Minimal kora.toml

[kora]
rate_limit = 100

[validation]
max_allowed_lamports = 1000000
max_signatures = 10
price_source = "Mock"  # or "Jupiter" (requires JUPITER_API_KEY env var)

allowed_programs = [
    "11111111111111111111111111111111",
    "TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA",
    "ATokenGPvbdGVxr1b2hvZbsiqW5xWH25efTNsLJA8knL",
    "ComputeBudget111111111111111111111111111111",
]

allowed_tokens = ["<your-token-mint>"]
allowed_spl_paid_tokens = ["<your-token-mint>"]

[validation.price]
type = "margin"
margin = 0.1  # 10% markup

Minimal signers.toml

[signer_pool]
strategy = "round_robin"  # or "random", "weighted"

[[signers]]
name = "signer_1"
type = "memory"
private_key_env = "KORA_PRIVATE_KEY"
weight = 1

Detailed References

• Full kora.toml reference: See references/configuration.md - all sections, fields, and production examples
• Signer types and setup: See references/signers.md - memory, Turnkey, Privy, Vault configuration
• Fee calculation and pricing: See references/fees.md - fee components, pricing models, security considerations

Key Operator Decisions

Pricing Model

Model	Use Case	Security
margin (default)	Charge users cost + markup	Safest - includes fee payer outflow
fixed	Flat fee per transaction	Must disable fee payer transfers in policy
free	Sponsor all fees	Must disable fee payer transfers in policy

Authentication

Three optional methods, can be used simultaneously:

• API Key: Simple x-api-key header. Set api_key in [kora.auth] or KORA_API_KEY env var.
• HMAC: Cryptographic signature with timestamp. Set hmac_secret in [kora.auth] or KORA_HMAC_SECRET env var.
• reCAPTCHA v3: Bot protection for signing methods. Set recaptcha_secret in [kora.auth] or KORA_RECAPTCHA_SECRET env var. Configurable recaptcha_score_threshold (default: 0.5) and protected_methods.

Fee Payer Policy

Control what actions the fee payer can perform in transactions. All default to false (restrictive). Explicitly set to true only what you need.

Critical for fixed/free pricing: ensure allow_transfer remains false (the default) on system and token programs to prevent fee payer fund drain.

Jito Bundle Support

Enable atomic multi-transaction execution via Jito:

[kora.bundle]
enabled = true

[kora.bundle.jito]
block_engine_url = "https://mainnet.block-engine.jito.wtf"

When using Jito tips paid by Kora, set allow_transfer = true in [validation.fee_payer_policy.system].

Lighthouse Fee Payer Protection

Adds balance assertion instructions to protect the fee payer from drainage attacks:

[kora.lighthouse]
enabled = true
fail_if_transaction_size_overflow = true

Only works with signTransaction/signBundle (not broadcast methods). Requires Lighthouse program in allowed_programs: L2TExMFKdjpN9kozasaurPirfHy9P8sbXoAN1qA3S95

Usage Limits

Rule-based per-user limiting with Redis backend:

[kora.usage_limit]
enabled = true
cache_url = "redis://redis:6379"
fallback_if_unavailable = false

[[kora.usage_limit.rules]]
type = "transaction"
max = 100
window_seconds = 3600

[[kora.usage_limit.rules]]
type = "instruction"
program = "TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA"
instruction = "Transfer"
max = 10
window_seconds = 3600

Requires user_id parameter in signing requests when enabled with free pricing.

Caching

Optional Redis caching for token account lookups:

[kora.cache]
enabled = true
url = "redis://localhost:6379"
default_ttl = 300
account_ttl = 60

Monitoring

Optional Prometheus metrics at /metrics:

[metrics]
enabled = true
endpoint = "/metrics"
port = 9090

Key metrics: kora_http_requests_total, kora_http_request_duration_seconds, signer_balance_lamports.

Deployment

Docker

Pre-built image available (tags: latest, beta, v<version>):

docker pull ghcr.io/solana-foundation/kora:latest
docker run -v ./kora.toml:/kora.toml -v ./signers.toml:/signers.toml \
  -e RPC_URL=https://api.mainnet-beta.solana.com \
  -e KORA_PRIVATE_KEY=<key> \
  -p 8080:8080 \
  ghcr.io/solana-foundation/kora:latest

Or build from source:

FROM rust:1.86-bookworm AS builder
RUN cargo install kora-cli
FROM debian:bookworm-slim
COPY --from=builder /usr/local/cargo/bin/kora /usr/local/bin/kora
COPY kora.toml signers.toml ./
ENV RPC_URL=https://api.mainnet-beta.solana.com
CMD ["kora", "rpc", "start", "--signers-config", "signers.toml"]

Railway

1. Create project with kora.toml, signers.toml, Dockerfile
2. railway login && railway init && railway up
3. Set env vars in dashboard: RPC_URL, KORA_PRIVATE_KEY, RUST_LOG
4. Generate public domain from settings

Docs: https://launch.solana.com/docs/kora/operators/deployment/railway

Kora Core Development

For contributors working on the Kora codebase itself:

just build          # Build all crates
just build-lib      # Build kora-lib only
just build-cli      # Build kora-cli only
just check          # Check formatting
just fmt            # Format + lint with auto-fix
just unit-test      # Run unit tests
just integration-test  # Run full integration test suite