Solana Foundation Kora 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:

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

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

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