10 API blockchain integration Interview Questions and Answers for api engineers

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1. Can you explain the difference between public and private blockchain?

Public and private blockchains differ mainly in their accessibility and permission systems. Public blockchains allow anyone to join and contribute to the network, while private blockchains restrict access to a select group of users or organizations. The level of transparency and decentralization also differs between the two types of blockchains.

  1. Public blockchains are more transparent than private blockchains. Transactions on public blockchains are visible to everyone on the network, and anyone can have access to the data. This makes them ideal for use cases where transparency and immutability are critical, such as supply chain management or banking.
  2. One disadvantage of public blockchains is that they can be slower and less scalable than private blockchains due to the large number of participants and the high level of network activity. Solving this problem is a major challenge for public blockchain developers
  3. Private blockchains, on the other hand, offer more privacy and security than public blockchains. Since only a limited number of users or organizations have access, private blockchains can offer faster and more efficient transactions.
  4. On a private blockchain, there is less need for a complex consensus mechanism since participants trust each other more. Thus, the network can operate more efficiently and with less energy consumption. However, private blockchains are less decentralized than their public counterparts, which can be an issue for some use cases.
  5. Overall, choosing between a public and private blockchain depends on the specific use case and requirements. Some projects may require high levels of transparency, while others may prioritize privacy and speed. Both types of blockchains have their advantages and disadvantages, which should be carefully evaluated before making a decision.

2. What is your experience with integrating APIs with blockchain technology?

Throughout my career as a software engineer, I have had the opportunity to work on several projects that required the integration of APIs with blockchain technology. In my previous role at Company A, I was responsible for developing a blockchain-based supply chain solution for a client in the manufacturing industry.

  • To accomplish this, I integrated APIs from several external vendors, such as IBM's Blockchain Platform and Ethereum's Solidity smart contract language, to build a secure, transparent and tamper-proof ledger for tracking the movement of products along the supply chain.
  • As a result of my work, the client was able to significantly reduce the time and costs associated with manual tracking and paperwork, resulting in a 25% increase in efficiency and 30% reduction in errors.

Additionally, I have also integrated APIs with blockchain technology to develop secure, decentralized voting systems for local and national elections. In one project, I integrated APIs from Ethereum and IOTA to enable secure and transparent voting through a distributed ledger, resulting in a successful election with over 10,000 voters from various locations in the world.

  1. The project was featured on several tech blogs and websites, and was even mentioned in a Forbes article on the future of voting technology.
  2. Overall, my experience with integrating APIs with blockchain technology has allowed me to develop innovative solutions that have delivered tangible results for clients across various industries.

3. How do you ensure the security of sensitive information when integrating blockchain and APIs?

Ensuring the security of sensitive information when integrating blockchain and APIs is critical in protecting our users' data. At my previous company, we implemented a multi-layered approach to ensure maximum security. Here are the steps we took:

  1. Encryption: All sensitive data was encrypted both at rest and in transit using strong encryption algorithms to prevent interception and unauthorized access. We used 256-bit Advanced Encryption Standard (AES) for data at rest and Transport Layer Security (TLS) with Perfect Forward Secrecy (PFS) for data in transit.
  2. Access Control: We implemented role-based access control (RBAC) to ensure that only authorized personnel had access to sensitive data. Passwords were stored using highly secure hashing algorithms, and we required two-factor authentication for all sensitive actions.
  3. API Security: We used API gateways to manage and secure API calls. The gateways served as a single point of entry, where we could implement authentication, rate-limiting, and other security mechanisms to prevent unauthorized access.
  4. Blockchain Security: We used a public blockchain platform that had strong security measures in place. We ensured that there were no weak links in the infrastructure by conducting regular security audits and performing vulnerability assessments.
  5. Testing: Finally, we tested our security measures regularly to ensure they were effective. We conducted penetration testing to identify vulnerabilities and ironed them out as soon as possible.

As a result of our efforts, we didn't experience any security breaches or data leaks. Our users' data was safe and secure, and they trusted us with their sensitive information.

4. Can you describe the role of smart contracts in blockchain integration?

Smart contracts play a crucial role in blockchain integration by allowing for automated transactions and agreements to occur without the need for intermediaries. Essentially, smart contracts are self-executing contracts with the terms of the agreement written into code.

This means that once certain conditions are met, such as the transfer of cryptocurrency, the smart contract is automatically triggered to carry out the agreed upon action. This not only saves time and resources, but also reduces the potential for fraud or conflict by removing the need for trust in intermediaries.

  1. For example, a smart contract can be used to automate the process of paying royalties to musicians on a music streaming platform. The smart contract would be programmed to pay out a certain percentage of revenue to each musician based on the number of plays their songs receive.
  2. Another example is the use of smart contracts in the supply chain industry. Smart contracts can be used to automatically track and verify the movement of goods across the supply chain, ensuring that all parties involved are in agreement about the location and condition of the products. This can help to reduce disputes and speed up the overall process.
  3. One study found that the use of smart contracts in supply chain management can lead to a 20% reduction in supply chain costs and a 50% reduction in lead times.

Overall, smart contracts are a powerful tool for enabling secure, automated transactions on the blockchain, and are essential for fully utilizing the potential of blockchain integration.

5. What are some common challenges you've faced when integrating APIs with blockchain, and how do you address those challenges?

One of the most common challenges I've faced when integrating APIs with blockchain is ensuring the security of sensitive data. With blockchain, data is immutable and irreversible, which makes it crucial to maintain data integrity and prevent unauthorized access.

To address this challenge, I always ensure that proper encryption and authorization protocols are in place, and limit access to the blockchain network to only authorized personnel. I also perform regular audits to identify any potential security vulnerabilities, and take swift action to rectify them.

Another challenge I've faced is managing the complex and often fragmented blockchain ecosystem, which can make it difficult to integrate APIs effectively. To overcome this, I rely on clear communication and collaboration with all stakeholders, including developers, business leaders, and external partners. This helps ensure a seamless integration that aligns with the needs of all parties involved.

Overall, my experience in integrating APIs with blockchain has taught me the importance of a structured approach that factors in all potential challenges and risks. By doing so, I can ensure that all integration efforts are successful and generate real value for the organization. For example, in a recent project I led, we successfully integrated blockchain APIs to streamline supply chain management, resulting in a 30% reduction in operational costs.

6. What are some best practices you follow when designing and developing API blockchain integrations?

When it comes to designing and developing API blockchain integrations, I follow several best practices:

  1. Clear documentation: I make sure to document every detail of the API blockchain integration process in a clear and concise manner so that other developers can easily understand and use it. I also create API reference documentation to save time and improve efficiency in the development process.
  2. Security: Security is of the utmost importance when it comes to blockchain. I make sure to follow best security practices when designing and developing the blockchain API integration to ensure the safety of data being shared. I use hashing algorithms, encryption protocols, and digital signatures to provide a high level of security in the integration.
  3. Scalability: Blockchain technology is growing rapidly and so, I make sure to design and develop the API integration with scalability in mind. I use design patterns such as microservices and containerization to make the integration scalable for future growth.
  4. Error handling: I design the API blockchain integration to handle errors efficiently. This includes implementing error codes, messages and logging, and retries for failed transactions. This ensures that any errors that occur during the integration process are promptly identified and resolved.
  5. Testing: Before releasing the API blockchain integration, I ensure that it passes a series of rigorous tests to confirm that it is working correctly. This includes functional testing, integration testing, and load testing to ensure that the integration works as expected and that it can handle a high volume of transactions.

As a result of following these practices, I was able to design and develop an API blockchain integration for a logistics company that improved their supply chain management system, allowing them to save 20% in transportation costs and reduce delivery times by 50%. The integration was also highly secure and scalable, handling a high volume of transactions with ease.

7. How do you ensure scalability and performance when integrating APIs with blockchain?

Scalability and performance are critical in API blockchain integration. To ensure scalability and performance, I follow the below approaches:

  1. Optimizing Node.js: I use Node.js as it enables non-blocking operations, which allows the application to handle numerous API requests simultaneously. Node’s event-driven framework results in faster execution and, as a result, improved application scalability and performance.
  2. Caching: I implement caching techniques to store the frequently requested data from the APIs, such as user data or market data. Retrieving frequently requested data from cache is much quicker than making another API call to get the same data. When I implemented caching techniques in a project, I noticed a 50% improvement in overall API response time and a 25% reduction in server load.
  3. Data Compression: Compressing response data can significantly improve the performance of the API. I use Gzip to achieve this. When I implemented this technique in the project I worked on, Gzip was able to compress the response data by up to 70%, resulting in a significant improvement in response time.
  4. Load Balancing: I use load balancing to distribute incoming API requests across multiple servers. This ensures that no one server is overloaded with requests, which can cause a slowdown. Implementing load balancing in the project I worked on helped to reduce server response times by 45%.
  5. Monitoring: Finally, I monitor the application's performance metrics regularly. This helps detect performance issues and bottlenecks, allowing for quick identification and resolution. When I noticed a spike in traffic that reduced the overall performance of the API, I quickly increased the number of servers allocated to the API, which led to an overall improvement in service response time within a few minutes.

These strategies have enabled me to ensure scalability and performance when integrating APIs with blockchain. As a result, I believe that I am well-positioned to succeed in roles that require expert knowledge of blockchain API integration.

8. What are the limitations of using blockchain in API integration?


  1. Scalability - Blockchain’s fundamental feature, its immutability, also poses a potential obstacle for scalability. As the network grows, the number of nodes that must process and store each transaction increases, slowing down the processing time. For example, in a stress test conducted by Visa with 1,700 transactions per second, Ethereum only managed 15 transactions per second.
  2. Cost - Another significant limitation is the cost. Because of its decentralization, blockchain requires significant amounts of resources to maintain and verify transactions. As a result, fees can accumulate quickly, becoming more expensive than traditional methods.
  3. Interoperability - The lack of standards for blockchain technology and lack of compatibility among different blockchain systems pose a problem with integration of blockchain and API. Developing integration tools to work with different blockchains can be costly and time-consuming.
  4. Regulations - Although blockchain technology is usually thought of as regulated and transparent, there are legal uncertainties. Within the blockchain industry, regulations tend to be unclear and change rapidly. Companies may find it challenging to navigate this regulatory landscape, which can limit their use of blockchain technology.
  5. Storage limits - Blockchains such as Bitcoin and Ethereum have finite storage capabilities. If developers want to integrate a large number of data and transactions outside the supported blockchain, they will need to supplement storage capacity which can be expensive.
  6. Speed - While the blockchain can guarantee a transaction’s authenticity and immutability, the verification processes usually take time. Higher transaction costs could make it prohibitively pricey to maintain transactions on the blockchain.
  7. Security - Blockchains are notoriously secure and immutable, but that doesn’t mean they’re infallible. In fact, blockchain hacks have happened in the past, often as a result of vulnerabilities in smart contracts—self-executing contracts that allow developers to automate transactions on the blockchain. Blockchain itself may be secure, but smart contracts are only as secure as their code.
  8. Privacy - All blockchain transactions are publicly visible, which can sometimes make privacy a concern. However, different blockchain platforms have started to experiment with solutions like masking user information and increasing privacy.
  9. Energy consumption - Blockchain technology uses a large amount of energy, the energy usage required to maintain the blockchain network is enormous. The environmental cost of running a blockchain platform can be high, and many companies are looking to greener alternatives to reduce energy consumption.
  10. Adoption - Perhaps the biggest limitation currently is the lack of adoption of blockchain technology in many industries outside of financial services. This means many companies are still exploring blockchain technology, and there may not be as many opportunities for integration as one would hope for.

9. What is your experience working with Ethereum, Hyperledger Fabric, and other blockchain platforms?

Throughout my career, I have had the opportunity to work with a variety of different blockchain platforms including Ethereum, Hyperledger Fabric, and others. In my previous position as a Blockchain Developer at a leading fintech company, I was responsible for designing and developing an Ethereum-based platform that enabled secure and transparent peer-to-peer transactions for our clients.

One of my key achievements during this time was implementing a smart contract that replaced a manual process for settling trades, resulting in a significant reduction in processing time and costs. Additionally, I collaborated with a cross-functional team to integrate Hyperledger Fabric into our platform, enabling us to provide clients with even greater transparency and security.

More recently, I worked on a blockchain-based supply chain management system using a combination of Ethereum and various other blockchain platforms. Through my expertise in using open-source blockchain protocols and technologies, I was able to design a system that improved traceability, efficiency, and transparency for all parties involved.

Overall, my experience working with various blockchain platforms has equipped me with a deep understanding of the advantages and limitations of each technology, allowing me to effectively design, develop, and deploy secure decentralization technologies that meet the specific needs of each project.

10. Can you walk me through the process of integrating a public blockchain API into an existing system?

Integrating a public blockchain API into an existing system requires careful planning and execution. Here's an outline of the process that I follow:

  1. Identify the blockchain platform to be used: Depending on the use case, different blockchain platforms may be more appropriate than others. For example, Ethereum is often used for smart contract applications, while Bitcoin is commonly used for financial transactions.
  2. Choose the API provider: Once the blockchain platform has been selected, an API provider needs to be chosen. Some popular providers include Etherscan, Infura, and Blockcypher.
  3. Retrieve API documentation: The API documentation is essential for understanding how to interact with the blockchain platform. I typically spend a few hours reading through the documentation and familiarizing myself with the various endpoints available.
  4. Create a test environment: Before integrating the API into the existing system, I create a test environment to ensure that everything works as expected. This involves setting up a mock blockchain network and performing some test transactions.
  5. Integrate the API: After completing the necessary testing, I begin integrating the API into the existing system. This typically involves modifying the code to include API calls and processing the blockchain data returned by the API.
  6. Test the integration: Once the integration has been completed, I conduct thorough testing to ensure that there are no bugs or errors. I also analyze the performance to ensure that the integration is efficient and effective.
  7. Deploy the integration: After all the necessary testing and debugging have been completed, I deploy the integration into the production environment. I closely monitor the system for any issues and make any necessary adjustments.
  8. Track the results: Finally, I track the results to ensure that the integration is meeting the expected goals. For example, if the goal was to increase efficiency, I might compare processing times before and after the integration.

Overall, the process of integrating a public blockchain API into an existing system requires careful planning, testing, and execution, but it can provide significant benefits in terms of security, transparency, and efficiency.


Congratulations on preparing yourself with the top API blockchain integration interview questions and answers for 2023. The next step in your job search is to write a cover letter that showcases your skills and experience. Our guide on writing a cover letter for API engineers can provide you with helpful tips and advice. Don't forget to check it out! Another vital step is to prepare an impressive CV that highlights your achievements. Our guide on writing a resume specifically for API engineers can help you craft an outstanding one. When you're ready to search for remote API engineer jobs, look no further than our job board at Remote Rocketship. We offer a wide range of exciting opportunities for backend developers. Good luck!

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