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Glossary

Quick reference for common terms used throughout Axol documentation.

Core Concepts​

API Key​

A unique identifier used to authenticate requests to the Axol API. Generated in your dashboard and included in request headers.

Compute Unit (CU)​

A measurement of computational resources (CPU, RAM, disk I/O, network) consumed by an API request. Different methods cost different amounts of CUs based on their complexity.

Examples:

  • eth_blockNumber: 10 CUs
  • eth_call: 26 CUs
  • debug_traceTransaction: 5,000 CUs

See Compute Units for details.

CUPs (Compute Units Per Second)​

Maximum throughput rate measured in CUs consumed per second. Controls how fast you can make requests. Also called "throughput limit".

Example: 10,000 CUPs = ~400 requests/second (assuming 25 CU average)

Monthly CU Pool​

Total compute units available per billing cycle. Separate pools exist for standard and trace methods. Resets on your billing date.

Trace CU Pool​

Separate CU allocation for high-compute trace and debug methods (trace_*, debug_*). Prevents accidental overages from expensive operations.

Rate Limiting​

Throughput Limit​

See CUPs above. The maximum rate at which you can consume CUs per second.

Soft Limit​

Warning threshold at which you receive alerts (typically 80-90% of your limit). No API restrictions yet.

Hard Limit​

Absolute maximum. Requests are throttled or rejected when reached (typically 100-110% of your limit).

Overage Billing​

Optional billing mode where you're charged for CUs consumed beyond your monthly pool, rather than being throttled. Available on paid plans - view pricing for details.

Methods & Operations​

Standard Methods​

Regular API methods like eth_*, net_*, web3_*. Low to medium CU cost (5-500 CUs). Count toward standard CU pool.

Trace Methods​

High-compute methods for transaction debugging (trace_*, debug_*). Very high CU cost (1,000-50,000 CUs). Count toward trace CU pool.

Examples:

  • trace_transaction: 1,000 CUs
  • debug_traceTransaction: 5,000 CUs
  • debug_traceBlockByNumber: 50,000 CUs

RPC (Remote Procedure Call)​

Standard protocol for interacting with blockchain nodes. Axol provides RPC endpoints for all supported chains.

WebSocket​

Real-time bi-directional communication protocol for receiving live blockchain data (new blocks, transactions, etc.). Each event costs 40 CUs.

Blockchain Terms​

Chain ID​

Numeric identifier for EVM-compatible chains (e.g., Ethereum = 1, Polygon = 137). Used to prevent transaction replay attacks.

API ID​

Axol's string identifier for chains in API calls (e.g., ethereum, polygon, bitcoin). More readable than chain IDs.

Archive Data​

Historical blockchain data beyond recent blocks. Availability varies by chain and tier:

  • Free/Starter: Last 30 days
  • Base: Last 90 days
  • Growth: Last 180 days
  • Scale+: Full history

Gas Price​

Cost to execute transactions on EVM chains, measured in gwei (1 gwei = 0.000000001 ETH). Axol provides real-time gas price data.

ENS (Ethereum Name Service)​

Human-readable names for Ethereum addresses (e.g., vitalik.eth → 0x...). Axol supports ENS resolution.

UTXO (Unspent Transaction Output)​

Bitcoin's transaction model. Each output can be spent once. Used for Bitcoin balance and transaction queries.

SPL Token​

Solana Program Library token standard, similar to ERC-20 on Ethereum.

Tiers & Pricing​

Tier​

Pricing level determining your CU allocations, features, and support level. Current tiers: Free, Starter, Professional, Business (max tier).

Overage Rate​

Cost per 1M CUs when you exceed your monthly pool (if overage billing enabled). View paid plans for current rates.

SLA (Service Level Agreement)​

Guaranteed uptime percentage:

  • Free/Starter: No SLA
  • Professional: 99.5%
  • Business (max tier): 99.9%

Error Codes​

401 Unauthorized​

Invalid or missing API key. Check authentication.

402 Payment Required​

Monthly CU pool exhausted. Enable overage billing or upgrade tier.

403 Forbidden​

API key lacks required scope/permission.

429 Too Many Requests​

Throughput limit (CUPs) exceeded. Implement backoff and retry.

500 Internal Server Error​

Server-side issue. Check status.axol.io or contact support.

Support & Resources​

Dashboard​

Web interface at app.axol.io for managing API keys, viewing usage, and configuring alerts.

SDK (Software Development Kit)​

Pre-built client libraries for Python and TypeScript/JavaScript that simplify API integration.

CU Calculator​

Tool for estimating monthly CU usage based on your expected API call patterns.

See also: