Chainstack Fundamentals Certification

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1. Why is embedding raw RPC keys directly in browser frontend code dangerous?

Modern browsers don't support making direct RPC calls to external blockchain endpoints

Anyone can view source code and extract keys to use your quota or abuse access

It makes the user interface harder to design and maintain across different browsers

It significantly slows down website loading due to additional cryptographic overhead

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2. Visit Developer portal and navigate to the Ethereum API reference. What is the JSON-RPC method name to get an account's ETH balance?

eth_balance

getBalance

eth_getBalance

eth_accountBalance

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3. What is the fundamental difference between collateralized stablecoins (like USDC) and algorithmic stablecoins?

Collateralized stablecoins are restricted to Ethereum while algorithmic work cross-chain

Algorithmic stablecoins consistently maintain tighter pegs due to automated mechanisms

There is no meaningful difference—both terms describe the same stabilization approach

Collateralized are backed by reserves; algorithmic use supply/demand mechanisms instead

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4. What is the primary technical tradeoff of public blockchains compared to private/permissioned chains?

Public chains use older cryptographic algorithms that are less secure but more widely supported

Public chains have higher transaction fees because of regulatory compliance requirements

Public chains sacrifice throughput and privacy for censorship resistance and open participation

Private chains require specialized hardware that limits throughput to maintain security

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5. What do Base, Unichain, and Zora have in common?

They are built on the OP Stack—Optimism's open-source rollup framework

They share a single sequencer operated by the Ethereum Foundation

They use zero-knowledge proofs exclusively, with no optimistic fraud proofs

They all run Solana's Sealevel VM for high-throughput transaction processing

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6. Why is it impractical to alter historical records on a public blockchain?

Blockchain foundations maintain encrypted master copies that reject unauthorized changes

The proof-of-work algorithm includes tamper-detection that invalidates altered blocks

Each block's hash depends on the previous block, so changing one requires re-mining all subsequent blocks

Government regulations and international treaties legally prohibit blockchain modifications

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7. Your team currently uses a single RPC key for dev, staging, and production, and it’s stored in a shared `.env` file that some developers have accidentally committed to Git before.

You want to improve your security posture without making development impossible.

Which approach is most appropriate?

Keep one key for all environments but encrypt the `.env` file and store it in the repo

Post the key in a team chat channel so it’s easy to copy-paste when needed

Use separate credentials per environment, store them in environment variables or a secrets manager, rotate them regularly, and enable IP allowlisting where possible

Move the key into the frontend code so everyone can easily access it when testing

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8. Why does geographic region selection matter for latency-sensitive applications?

It doesn't matter since blockchain networks are inherently decentralized globally

Some blockchains only exist in certain geographic regions due to regulations

Different regions have different pricing tiers based on local infrastructure costs

Network latency increases with distance; closer nodes reduce round-trip time

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9. Run the following curl command to query an Ethereum node:

bash
curl -X POST https://ethereum-mainnet.core.chainstack.com/2f6d649e68c2f861fecd5b8a9e35139e \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}'

What decimal value does Ethereum mainnet's chain ID represent?

42161

56

137

1

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10. What makes Chainstack's Solana Geyser streaming offering notable?

It's exclusively available to enterprise customers on dedicated plans

It only works on Solana testnet environments, not mainnet production

It offers the widest range of tiers in the industry at competitive pricing

It's the only provider offering Geyser streaming for Solana blockchain

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11. What technical foundation dominates the multi-chain landscape?

EVM and Geth—most chains are EVM-compatible or run clients derived from go-ethereum

Bitcoin Script and Bitcoin Core—all programmable blockchains are direct Bitcoin forks

Each chain developed completely independent execution environments and clients

Solana's Sealevel VM became the industry standard that most new chains now adopt

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12. What is "gas" in the context of blockchain transactions?

The electrical energy consumed by mining hardware measured in kilowatt-hours

A unit measuring computational effort required to execute operations, paid as fees

A token type that validators stake to participate in block production and consensus

The network bandwidth required to propagate transactions across nodes globally

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13. Your application starts returning 429 errors during peak traffic. Before requesting a plan upgrade, what optimization should you evaluate first?

Deploy additional endpoints in different geographic regions

Implement caching for static data and batch multiple calls into single requests

Reduce your application's functionality to decrease blockchain interactions

Switch from HTTPS to WebSocket connections exclusively

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14. Which description best matches Chainstack's Global Nodes offering?

A client-side JavaScript library that automatically retries failed RPC requests

Testnet-only endpoints that are not suitable for production traffic

Globally distributed, geo-load-balanced shared infrastructure for general-purpose workloads

Single-tenant dedicated nodes reserved for a single customer with custom hardware

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15. What type of data can you receive through WebSocket subscriptions?

Exclusively smart contract events without block or transaction updates

Only account balance changes when tokens are transferred to/from addresses

Real-time updates: new blocks, pending transactions, logs, and state changes

Only historical data that can be queried through standard RPC methods

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16. A DeFi team is choosing between an EVM L2 (like Arbitrum) and a high-throughput non-EVM chain (like Solana). Which tradeoff assessment is most accurate?

EVM L2 enables Solidity reuse and Ethereum liquidity access; non-EVM offers throughput but needs new tooling

Both options provide identical developer tooling and equivalent liquidity access across ecosystems

EVM L2s cannot support DeFi applications due to fundamental technical limitations in rollup design

Non-EVM chains consistently provide deeper liquidity pools than any Ethereum Layer 2 solution

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17. For most new projects, what is a sensible way to use Chainstack’s free Developer plan (3M monthly requests) in their rollout?

Only use it for non-blockchain experiments, since it doesn't expose real RPC endpoints

Use it indefinitely for production; it is designed to handle any scale

Skip it and go straight to high-tier nodes; the Developer plan is only for tutorials

Use it to build and validate a proof of concept or MVP, then move to higher tiers once traffic, latency needs, or team size outgrow the free quota

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18. A security researcher needs to replay a suspicious transaction from 6 months ago to analyze its exact execution path, including internal calls and state changes. What Chainstack capabilities do they need?

Archive node with debug & trace APIs—stores historical state and can replay transaction execution

WebSocket subscription—streams real-time events as they occur on the network

Trader Node with Warp transactions—optimizes transaction propagation speed to validators

Global Node in full mode—provides fast access to recent blocks and pending transactions

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19. When a team adopts Chainstack instead of running its own blockchain nodes, which responsibility most clearly remains with the team (not Chainstack)?

Monitoring node health, disk usage, and consensus participation

Designing, building, and maintaining their dApp business logic and smart contracts

Provisioning and scaling underlying compute and storage for nodes

Keeping node software up to date and highly available across regions

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20. What is the difference between an execution client and a consensus client in post-merge Ethereum?

Consensus clients run only on testnets while execution clients operate on mainnet

They are identical software packages distributed under different names for licensing reasons

Execution handles transactions and state; consensus handles proof-of-stake and block proposals

Execution clients were deprecated after the merge and replaced by consensus clients

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21. What role does a node play in a blockchain network?

Nodes store compressed historical data for archival and regulatory compliance purposes

Nodes exclusively handle payment routing between different wallet addresses on the network

Nodes serve as optional caching layers that improve query performance for applications

Nodes maintain blockchain state, validate transactions, and provide data access for applications

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22. A team is evaluating RPC providers for their production dApp. They want objective performance data—response times, success rates, and block delays—across providers and regions. What Chainstack tool helps with this?

Chainstack Compare—an open-source benchmarking dashboard that measures RPC provider performance

Chainstack MCP—Model Context Protocol integration for AI agents

Chainstack Platform API—programmatic access to manage Chainstack resources

Chainstack Console—the dashboard for deploying and managing your own nodes

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23. What is the key difference between HTTP RPC endpoints and WebSocket endpoints?

HTTP provides stronger encryption and authentication than WebSocket connections

HTTP endpoints consistently deliver faster response times than WebSocket connections

WebSocket connections are restricted to read-only operations for security reasons

HTTP is request-response; WebSocket maintains persistent connections for real-time updates

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24. A successful analytics product built on Chainstack now serves dashboards for thousands of users. Metrics show a steady load of ~400 requests per second during business hours, with very little traffic overnight. The team wants to stop worrying about per-request costs and have a predictable monthly bill while keeping this throughput. Which Chainstack option best fits their needs?

Move everything to Trader Nodes, which are optimized only low latency and still billed per request

Switch to Dedicated Nodes only; tenant isolation automatically makes all calls free within that environment

Stay on pay-as-you-go Global Nodes and accept variable monthly cost based on exact request volume

Use an Unlimited Node at an appropriate RPS tier so calls are effectively unlimited up to that throughput for a flat monthly price

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25. What is the difference between eth_call and eth_sendTransaction?

They are identical methods—the naming difference is purely for backward compatibility

eth_call reads data without changing state (free); eth_sendTransaction modifies state (costs gas)

eth_sendTransaction is exclusively for transferring ETH between wallet addresses

eth_call executes faster because it bypasses the mempool and validator queue

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26. A DeFi protocol has two components: a public-facing dApp serving users worldwide that needs high availability, and an internal liquidation bot that must execute transactions faster than competitors. How should they architect their Chainstack infrastructure?

Global Nodes for the dApp (geo-distributed availability) and Trader Nodes for the liquidation bot (regional low-latency)

Use only Global Nodes—they automatically optimize for both latency and availability simultaneously

Dedicated Nodes are required for any production workload regardless of requirements

Use Trader Nodes for everything—low latency benefits all components equally

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27. For which use case would Trader nodes be the best choice?

Archival data research requiring historical state queries

Low-frequency data queries for backend analytics dashboards

Latency-sensitive DeFi trading requiring fast execution speeds

Development and testing environments with moderate traffic loads

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28. A project has outgrown Chainstack's free Developer tier and is evaluating paid options. Their traffic fluctuates significantly—some hours they need 200 RPS, other times nearly zero. What is a key advantage of staying on pay-as-you-go Global Nodes rather than committing to a fixed RPS tier?

They avoid paying for unused capacity during low-traffic periods

Fixed RPS tiers don't support WebSocket connections

Pay-as-you-go nodes are deployed in more geographic regions

Pay-as-you-go provides faster response times than fixed-tier nodes

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29. A trading firm is selecting an RPC infrastructure provider for latency-sensitive arbitrage. What infrastructure features should they prioritize?

Built-in wallet management and fiat on-ramp integrations for retail user onboarding

Co-location near validators, dedicated nodes, low-latency routing

Largest free tier allocation and most generous rate limits for cost optimization

Support for the widest range of testnets and development-focused debugging tools

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30. What is the difference between a validating node and a non-validating (RPC) node?

Validating nodes secure the network through consensus; RPC nodes only provide data access

Validating nodes process transactions faster due to their direct connection to the mempool

All nodes perform validation; the terms just describe different configuration settings

Non-validating nodes store complete historical state while validators only keep recent data

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31. A DevOps team wants to automate their infrastructure: spinning up nodes for new chains, listing all endpoints across projects, and integrating node deployment into their CI/CD pipeline. What Chainstack capability enables this?

Chainstack Console—the web dashboard for manual node management

WebSocket endpoints—for subscribing to real-time blockchain events

Chainstack Platform API—RESTful API for programmatic resource management

Chainstack Compare—benchmarking tool for evaluating RPC providers

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32. Why can't a smart contract directly fetch data from an external API (like a price feed)?

Blockchain execution must be deterministic—different nodes could get different API responses

Network validators block all outbound HTTP requests at the protocol level for security

Smart contract bytecode doesn't include networking libraries in the EVM specification

External API calls would add unpredictable latency that could cause transaction timeouts

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33. Your team is launching a marketing campaign next week that could double or triple your normal traffic. What should you do to prepare your Chainstack infrastructure?

Nothing—Chainstack automatically scales infinitely with no plan limits

Review your current usage against plan limits, upgrade if needed, and set up alerts to catch issues early

Delay the campaign until you can build your own node infrastructure from scratch

Switch to a different blockchain that can handle more transactions per second

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34. A DeFi analytics startup queries historical data across Ethereum, Arbitrum, and Base. They need reliable access but don't require ultra-low latency. Which Chainstack node type best fits their use case?

Global Nodes—geo-load-balanced endpoints with automatic failover

Trader Nodes—optimized for latency-sensitive transaction execution

Dedicated Nodes—single-tenant infrastructure with custom hardware specs

Validator Nodes—for participating in consensus and earning staking rewards

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35. What is an RPC endpoint in Web3 development?

A local development server that simulates blockchain behavior for testing purposes

A URL providing an API interface to query blockchain nodes and submit transactions

A WebSocket-only protocol designed for real-time blockchain event subscriptions

A peer-to-peer network address that connects your application directly to validators

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36. Match the Chainstack node type to its defining characteristic:

1. Trader Node

2. Dedicated Node

3. Unlimited Node

4. Global Node

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37. What is a node client in Ethereum?

A browser extension that connects websites to the user's cryptocurrency wallet

Software implementing the Ethereum protocol, allowing a computer to operate as a node

A mobile or desktop application that lets users check balances and send transactions

A development framework for writing, testing, and deploying smart contracts locally

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38. A trading firm's infrastructure has grown: they now run 5 trading bots at 100+ RPS each, require custom node configurations, and need guaranteed isolation from other customers' traffic. Which Chainstack option addresses these enterprise requirements?

Unlimited Nodes—flat-fee pricing automatically provides tenant isolation

Dedicated Nodes—single-tenant infrastructure with custom configurations

Trader Nodes with Warp transactions for all bots

Multiple Global Node endpoints—one per bot for traffic separation

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39. Cross-chain bridges enable asset transfers between blockchains. What is a critical consideration when using them?

All bridges use identical security models since they're standardized by Ethereum governance

Bridges are completely trustless with no additional risk beyond normal blockchain usage

Bridges can only transfer NFTs between chains, not fungible tokens or native assets

Bridge security varies by design; bridge exploits have caused some of DeFi's largest losses

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40. A trading firm wants their arbitrage bot's transactions to reach validators faster than standard P2P propagation. What Chainstack feature addresses this?

Warp transactions—routes `eth_sendRawTransaction` through bloXroute's high-speed relay network

Debug & Trace APIs—replays transactions to analyze execution

Archive mode—stores historical state for querying past blocks

WebSocket subscriptions—streams real-time events from the mempool

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41. Put these steps of a typical blockchain transaction lifecycle in the correct order:

1. Transaction is included in a block
2. User signs transaction with private key
3. Transaction is broadcast to the network
4. Validator selects transaction from mempool
5. Block is validated by consensus mechanism

2, 4, 3, 1, 5

3, 2, 4, 1, 5

2, 3, 1, 4, 5

2, 3, 4, 1, 5

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42. What strategies can help reduce costs when using Chainstack?

Run your own full node infrastructure to eliminate all third-party costs

Only use mainnet for all development, testing, and production traffic workloads

Use dedicated nodes for every workload to ensure you never hit shared rate limits

Optimize requests (batch calls, cache responses), right-size plans, use testnets for dev

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43. Why is EVM compatibility significant for the multi-chain ecosystem?

It makes Ethereum process transactions faster by distributing load across compatible chains

It provides a standard runtime—same contracts deploy on Ethereum, Polygon, Arbitrum, or Base

It eliminates gas fees by standardizing transaction costs across all participating networks

It's mandated by international cryptocurrency regulations for cross-border transactions

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44. When evaluating a DeFi protocol or blockchain ecosystem, what does TVL (Total Value Locked) indicate?

The total number of unique wallet addresses that have ever transacted on the network

Capital committed to protocols, reflecting user trust, adoption, and available liquidity

The maximum transactions per second the network can theoretically process at peak

The total market capitalization of all tokens that have ever been issued on that chain

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45. Which pairing correctly matches each chain with its execution environment?

Ethereum → EVM, Solana → SVM, Aptos → MoveVM, Hyperliquid → HyperCore + HyperEVM

Ethereum → EVM, Solana → EVM, Aptos → MoveVM, Hyperliquid → MoveVM

Ethereum → SVM, Solana → EVM, Aptos → EVM, Hyperliquid → EVM only

Ethereum → EVM, Solana → MoveVM, Aptos → SVM, Hyperliquid → SVM

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46. You call a JSON-RPC method on a Chainstack endpoint and get an error like `the method does not exist / is not available`. What is the first place you should check to understand where the issue stems from?

Your frontend framework documentation to check for known bugs in HTTP request handling

The node client's official documentation or GitHub repository to confirm whether the method is implemented for that client and protocol

The Chainstack pricing page to see if the method is only available on higher plans

Social media to see if other developers are complaining about the same error

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47. Your dApp users report that the app is "sometimes slow." Your metrics show most requests complete quickly, but a small percentage take much longer. Error rates are normal. What does this pattern most likely indicate?

The blockchain network is globally congested and affecting all applications equally

Certain types of requests (like complex queries) are slower—investigate which specific operations are affected

Your credentials have been compromised and someone is abusing your quota

The endpoint is down and needs immediate replacement

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48. Chainstack uses two distinct types of credentials. What is the difference between a Platform API key and node endpoint credentials?

They're identical—both authenticate RPC requests to blockchain nodes

Platform API key is for testnet only; endpoint credentials are for mainnet production use

Platform API key is deprecated; all authentication now uses endpoint credentials exclusively

Platform API key manages Chainstack resources (projects, nodes); endpoint credentials authenticate blockchain RPC requests

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49. Where does a block explorer like Etherscan get its blockchain data?

Through a peer-to-peer protocol that aggregates queries across multiple block explorers

By running their own nodes and indexing blockchain data into queryable databases

By licensing pre-indexed datasets from cryptocurrency exchanges and data providers

From the Ethereum Foundation's centralized API that aggregates data from all validators

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50. In blockchain wallet management, what is the relationship between a private key and a public key?

Both keys are generated independently and then linked together during wallet creation

The public key is mathematically derived from the private key using one-way cryptography

The private key is derived from the public key through a reversible encryption process

They are identical values stored in different formats for compatibility with various systems

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51. What is MEV (Maximal Extractable Value)?

The aggregate total value locked across all DeFi protocols on a given blockchain

The maximum amount of ETH that any single wallet address can hold at one time

The maximum gas limit that can be set for any individual block on the network

Profit block producers extract by strategically reordering or excluding transactions

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52. Examine this Solana RPC call that simulates a minimal SOL transfer:

bash
curl -X POST https://solana-mainnet.core.chainstack.com/83e0d6661ee0488e22e167c18818cb38 \
-H "Content-Type: application/json" \
-d '{
"jsonrpc":"2.0",
"id":1,
"method":"simulateTransaction",
"params":[
"AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAAEDqMwrJgPrz9mUBsguLLK4z7c2rLvNsJP0zjb+oqEJILEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMhKzIsAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAgAADAIAAAAAAAAAAAAA",
{"encoding":"base64","replaceRecentBlockhash":true}
]
}'

What does simulateTransaction provide, and why is it essential for Solana development?

Broadcasts the transaction to validators and waits for finalized confirmation

Subscribes to the mempool and streams pending transactions in real-time

Executes the transaction locally without broadcasting—returns logs, compute units consumed, and errors

Queries historical transactions and returns decoded instruction data for analytics

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53. Why would you need an archive node instead of a full node?

Full nodes cannot interact with smart contracts or execute eth_call requests

To query historical state like "what was this account's balance 2 years ago?"

Archive nodes require less storage space through advanced compression algorithms

Archive nodes provide faster response times for real-time transaction monitoring

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54. What are events and logs in Ethereum smart contracts?

Data emitted by contracts, stored in receipts, and indexed for efficient off-chain querying

Debug information stored privately on-chain, only visible to the contract deployer

Error messages generated when transactions fail due to reverts or out-of-gas conditions

Console output from the EVM that developers can view during local testing and debugging

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55. What makes mainnet ETH valuable while Sepolia testnet ETH is worthless, despite both networks running the same protocol?

Testnet tokens have built-in protocol restrictions that prevent transfers to exchanges

Mainnet uses stronger cryptographic algorithms that provide additional security guarantees

Value emerges from social consensus—markets and users collectively treat mainnet as "real"

Mainnet processes transactions significantly faster due to higher validator participation

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56. A Web3 startup is launching a DeFi protocol with these requirements:

Public-facing dApp serving users in Asia, Europe, and North America
Liquidation bot that needs transactions to reach validators faster than competitors
Analytics dashboard querying 6-month historical data across Ethereum and Arbitrum
Limited initial budget, but infrastructure must scale if the protocol succeeds

Which infrastructure approach addresses all these requirements?

Trader Nodes for all components—low latency benefits everything equally

Free tier endpoints only—upgrade to paid infrastructure after reaching product-market fit

Dedicated Nodes for everything—a single premium solution covers all needs

Global Nodes for the dApp, Trader Nodes with Warp transactions for the bot, archive access for analytics, starting on pay-as-you-go and scaling as needed

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57. A dApp serves users in Tokyo, London, and New York. During a major token launch, traffic spikes 10x globally. Users in all regions continue experiencing low latency. What Chainstack Global Node behavior explains this?

The dApp's frontend includes custom load-balancing code that rotates between hardcoded endpoints

Chainstack rate-limits all users equally during spikes to prevent any single region from overloading

Geo-load balancing distributes requests across the nearest healthy nodes, scaling elastically with demand

Developers must pre-provision additional regional endpoints before anticipated traffic spikes

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58. How is Chainstack's pricing primarily calculated?

Based on the number of requests made to the RPC endpoints (usage-based)

Based on the number of individual nodes you have deployed in your account

A flat monthly subscription fee regardless of how much you actually use

Determined solely by which blockchain protocols you're accessing

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59. In the Chainstack console, what kind of information can you typically see on an endpoint’s metrics/usage dashboard?

Request volume, latency percentiles, error rates, and rate-limit hits over time

On-chain token balances for all addresses that used the endpoint

Only the total number of API keys created in the organization

Full smart contract source code and verified ABI for deployed contracts

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60. What is the relationship between Layer 1 (L1) and Layer 2 (L2) in blockchain architecture?

L1 handles user transactions while L2 is the internal validator communication layer

L1 processes smart contracts while L2 exclusively handles simple token transfers

L1 is the base blockchain (e.g., Ethereum); L2s are scaling solutions built on top of L1

L1 and L2 are interchangeable terms for a blockchain's mainnet and testnet networks