Learn / Beginner · Foundations
Blockchain versus a normal database
Beginner · Foundations · about 3 min read
Both store records, but a normal database has one owner who can change it, while a blockchain is shared by many computers and is built so that past records are very hard to change.
How they differ
- Who is in charge. A normal database has an administrator with authority to create, change and delete data, so users have to trust that owner. A blockchain is copied across many independent computers and usually has no central authority such as a bank, a company or a government.
- How records change. A normal database can overwrite or erase a record. A blockchain is append-only: a correction is added as a later record, so the full history stays. Blocks are linked by hashes, so altering one block changes every block after it. NIST calls blockchains tamper evident and tamper resistant, which is not the same as impossible to change.
- Who you must trust. A blockchain is designed for people who do not know or trust each other, because shared rules and consensus replace a trusted middleman. A private blockchain where one entity decides who can add records brings the trust question back, because users must trust that entity.
- Speed and cost. Getting many computers to agree takes time and effort. Proof of work uses a lot of computing power, so a blockchain is usually slower and costlier than a normal database doing the same job.
When each fits
- A blockchain can suit a record shared by many people who have no trusted third party, such as transferring digital assets or keeping a shared history of who owned what.
- A normal database usually suits a job where one organisation is trusted to run it and speed and privacy matter, such as a shop’s stock list.
Keep in mind
- A blockchain is not automatically better. NIST says it is “not magical” and will not solve every problem.
- Not every blockchain is open to all. Some let only approved parties add records.
- For the basics, see What is a blockchain? and What does “decentralised” mean?
- General information, not financial advice.
Key terms
Database, ledger, append-only, node, consensus, hash.
Module quiz
3 questions. Tap an answer to see if you are right and why. Get 2 right to complete the module.
1. Who controls a normal database?
A normal database has one party in charge, so users trust that party.
2. What does append-only mean for a blockchain?
A change is recorded as a later entry, so the history stays.
3. Why is a blockchain usually slower and costlier than a normal database?
Reaching agreement across many computers takes time and effort.