A signup system answers three separate questions: which account a person or client controls, what optional information belongs to that account, and which other accounts it may connect to. Each answer gets its own table, check, and access rule. The right design depends on what the account protects and what the relationships mean, so there is no single signup flow or schema that fits every service.
This guide assumes a conventional relational database and a web service that stores users, optional profiles, and user-to-user links. It is platform-neutral and does not assume a particular language, framework, or authentication protocol. Where the examples use SQL, they are illustrative sketches to adapt, not tested migrations.
As an Amazon Associate I earn from qualifying purchases.
Start with what an account identity means
A digital identity is unique within your service, but it does not have to identify a real-world person. Your users record is an account identity. Authentication is the process of checking that whoever is calling your system controls that identity, using one or more authenticators such as a password, a one-time code, or a passkey. Identity proofing is a different question: whether the account is bound to a real person, and how strongly you have checked it.
Keeping these apart prevents a common mistake. Verifying that someone controls an email address proves control of that address. It does not prove the person’s legal name, age, or eligibility. OWASP’s authentication guidance makes the same distinction and permits email as a username when the address is verified during signup, while recommending that users can also pick a non-email username.
Two identifiers are useful here. Keep an internal numeric key for joins and foreign keys, and give each user a random public identifier for URLs and API responses. OWASP advises that user IDs should ideally be randomly generated, because sequential IDs can be guessed or inferred from exposed data.
Decide signup requirements from risk
Signup rules should follow from what the account can do. Before writing the form, answer these questions in writing:
- Who may register: anyone, invited users only, or users from a specific organization?
- Is approval manual, automated, or absent?
- May one real-world identity hold several accounts, and may users choose their own roles?
- What proof is required at signup, and how is it checked?
- Which identity attributes are verified, and which are self-declared?
OWASP’s registration guidance frames these as questions to align with business and security requirements, and it recommends testing the registration path for forged identity data and manipulated requests, such as a client that submits a role or verified flag it should not control.
Recommended Free Tools
The following table compares common levels of assurance. The right row depends on the account’s impact, not on what is easiest to build.
| Approach | What it establishes | Typical fit | Trade-offs |
|---|---|---|---|
| Email ownership confirmation | The registrant controls the address at the time of verification | Low-impact community accounts, comment or preference features | Low friction; does not establish legal identity, and disposable addresses can still pass |
| Manual or invitation-based approval | A staff member or existing member vetted the registrant | Internal tools, invite-only groups, small professional communities | Strong human vetting; adds operational queues and response delays |
| Stronger identity proofing | The account is bound to a real person to a defined assurance level | Regulated or high-impact access, such as financial or government services | Higher friction and data-handling obligations; the applicable rules are set by your jurisdiction and sector, not by this guide |
For the stronger tier, NIST’s SP 800-63-4 suite is a useful structured reference. It covers identity proofing, enrollment, authenticators, and federation. Its companion SP 800-63A-4, which focuses on identity proofing and enrollment, defines three identity assurance levels and was published in final form on July 31, 2025. NIST states that these guidelines are written for government information systems and are not meant to constrain standards outside that purpose. Consumer services can borrow the vocabulary, but should not claim that NIST prescribes their signup flow. NIST’s abstract describes its scope as covering “the identity proofing, authentication, and federation of users (e.g., employees, contractors, or private individuals) who interact with government information systems over networks.”
Build the signup and verification flow
For a low-impact account where email ownership is the verification step, a sound flow looks like this:
- Accept the registration request and validate the email format. Store the address in normalized form, such as lower-cased, and reject it if it already belongs to a verified account.
- Create the user with a status such as
pending_verification. Do not grant any product permissions yet. - Generate a random, single-use verification token. Store only a hash of it, set an expiry, and send the raw token in a link or code to the address.
- When the token is presented, check that it is unexpired and unused, mark the email as verified, and set the account status to active in the same transaction.
- Return the same generic response for every signup request, whether or not the address already exists, and send an “already registered” notice by email rather than in the response.
Two failure modes deserve explicit handling. If the token is accepted twice, a race condition can activate the account twice or log a duplicate event, so make the state change conditional on the token still being unused. If verification mail is delayed, users will retry; the resend path should be rate-limited so it cannot be used to flood an inbox or enumerate accounts.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsStore users and optional profiles
Keep the account and the profile conceptually distinct
An account holds stable identity and account state: credentials or authenticator references, verification status, locks, and audit timestamps. A profile holds descriptive, user-facing attributes such as a display name, biography, or avatar. Separating them is not mandatory, but it is useful when some users have no profile, when profile data has different visibility or access rules, or when the profile changes far more often than the account.
Rank #3
Enforce one profile per user with a unique foreign key
When profiles are separate, the profile row references its user with a foreign key. Adding a uniqueness constraint to that key allows at most one profile per user, while a user can exist without any profile. The foreign key ensures every profile points to a real user.
CREATE TABLE users (
id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
public_id UUID NOT NULL UNIQUE DEFAULT gen_random_uuid(),
email TEXT NOT NULL UNIQUE,
status TEXT NOT NULL DEFAULT 'pending_verification',
created_at TIMESTAMPTZ NOT NULL DEFAULT now()
);
CREATE TABLE profiles (
id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
user_id BIGINT NOT NULL UNIQUE REFERENCES users (id) ON DELETE CASCADE,
display_name TEXT NOT NULL,
bio TEXT
);The ON DELETE CASCADE clause is one deletion policy among several. It is appropriate only if deleting an account should also delete its profile; the next section covers why that decision belongs to the domain, not the database.
When one table is enough
A one-to-one relationship does not always need two tables. Microsoft’s database design guidance notes that a one-to-one relationship can sometimes be combined into a single table. Combine them when the profile is always present, has few fields, and shares the same access rules as the account. Split them when optionality, visibility, or change frequency differ.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →| Option | Fits when | Watch for |
|---|---|---|
| Single table for account and profile | Every user has a profile, few fields, and one access policy | Public-facing fields and internal account state sit side by side, so accidental over-selection exposes more than intended |
Separate profile table with a unique user_id |
Profiles are optional or have distinct visibility rules | An extra join on reads; the application must create profiles and handle users who have none |
Separate table with no uniqueness on user_id |
Not a one-profile model; only suitable if multiple profiles per user are intended | Duplicates can appear unless the application enforces its own rules, so name the intent explicitly |
Model relationships between users
Use a join table for many-to-many links
When a user can connect to many users and vice versa, store each link as a row in an association table with a foreign key to each side. A composite primary key or an equivalent uniqueness constraint prevents duplicate pairs. PostgreSQL’s documentation illustrates this pattern and explains that foreign keys restrict associations to rows that actually exist.
Rank #4
![AutoCAD Architecture 2022 Software [Single User]](https://m.media-amazon.com/images/I/41RIhD2kbyL._SL160_.jpg)
- Perpetual Full Version. No subscription, no additional fees. Online account not included, so no Tech support . For Win-11 and 10 64-Bit Machines Only
- Extended Data Properties in a Shared View: Extract more object properties from a shared view of a drawing.
- 3D Graphics Technical Preview: Includes a technical preview of a new cross-platform 3D graphics system for smoother navigation of larger drawings.
- Purge Invisible AEC Data: Successfully save an AutoCAD drawing to a previous version by purging the invisible AEC data. -
- Push to Autocad Docs: Allows teams to upload AutoCAD drawings as PDFs to a specific project on Docs for easy reference in the field.
CREATE TABLE connections (
requester_id BIGINT NOT NULL REFERENCES users (id) ON DELETE CASCADE,
addressee_id BIGINT NOT NULL REFERENCES users (id) ON DELETE CASCADE,
status TEXT NOT NULL CHECK (status IN ('pending', 'accepted', 'blocked')),
created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
PRIMARY KEY (requester_id, addressee_id),
CHECK (requester_id <> addressee_id)
);The schema above is directional: Alice-to-Bob and Bob-to-Alice can both exist as separate rows. That may be what a follow feature needs. A mutual friendship usually needs a different rule, such as storing the pair in a canonical order or adding a unique index over the pair regardless of direction. The database cannot choose between these; the product must.
Settle the domain rules before the schema
Database constraints enforce structure but not meaning. Before writing the migration, decide:
- Symmetry: is the link mutual, or one-way?
- Consent: must both users agree before the link becomes active?
- Visibility: does one side’s block or privacy setting hide the other side’s profile?
- Deletion: when an account is deleted, should links cascade away, be retained for history, or be restricted until they are removed? Each choice has different consequences for other users and for audit needs.
Promote the link to an entity when it carries meaning
A link that is only “these two users are connected” can stay a plain join table. Once the association has its own facts, treat it as a first-class relationship record with its own columns, lifecycle, and history.
| Association feature | Plain join table is likely enough | Promote to a relationship entity |
|---|---|---|
| Direction | Not meaningful, or represented by column order | Requester and addressee roles matter to the product |
| State | Exists or does not exist | Pending, accepted, declined, blocked, or revoked |
| Timestamps | Not needed | Invitation sent, accepted, or ended; used for ordering or audit |
| Recurrence | A single link per pair | The same pair can connect, disconnect, and reconnect, with history kept |
| Provenance | Not tracked | Source of the link, such as an invitation code or import, is recorded |
This promotion is a design judgment. The data model supports it, but the decision rests on whether the attributes describe the association itself rather than either user.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Stop users reading or changing other users’ records
Check the object against the authenticated account every time
Authorization must check the requested record against the authenticated account on each read and write. OWASP’s guidance on insecure direct object references warns that changing a user ID in a request can expose or modify another person’s profile when the server does not check ownership. An unguessable identifier helps as defense in depth, but it does not replace the permission check.
- Derive the acting user from the server-side session or verified token, never from a field in the request body.
- Look up the target record by its identifier and compare it with the acting user, or with the relationship rules that grant access.
- Return the same “not found” response for records the caller may not see, so the endpoint does not reveal which identifiers exist.
- Repeat the check for every mutation, including bulk endpoints, exports, and background jobs that act on behalf of a user.
A profile update can be written so that ownership is part of the statement itself:
UPDATE profiles
SET display_name = $1, bio = $2
WHERE user_id = $3; -- $3 is the session's user id, not a request parameterIf the statement affects zero rows, the caller either has no profile or is not the owner, and the response should not distinguish the two cases.
Free tools Windows power users keep installed
One-click scans. No signup required.
Keep failure responses generic
Signup, login, and account recovery are common places where an application reveals whether an account exists. OWASP’s digital identity developer guidance advises generic failure behavior that does not expose whether a username exists, including through response timing. Apply the same rule to verification resends and password recovery, where a helpful-sounding message can leak the same information.
Protect credentials and database access
Database credentials belong outside source control, in a secrets store or environment configuration that is injected at runtime. Application accounts should be least-privilege: grant only the schemas, tables, and operations each service needs, and restrict connections to the hosts that require them. OWASP’s database security guidance recommends limiting privileges and access scope in this way.
A practical split is a migration role that can change schema, and an application role that can only select, insert, and update the tables it uses. The application role should not be able to alter the schema or read tables belonging to other services.
Choose between building and buying authentication
An in-house system gives full control over the schema and flow but makes your team responsible for credential storage, rate limiting, verification delivery, recovery, and keeping up with current guidance. A managed identity service shifts much of that operational work to a provider, at the cost of an external trust boundary and integration constraints. Compare the two on operational responsibility, integration needs, and where user data is processed. Whichever you choose, the account, profile, and relationship rules described above still belong in your own data model, because they encode your product’s meaning.
Quick Recap
Checklist before you ship signup
- Account identity, authentication, and identity proofing are documented as separate decisions.
- Signup requirements match the account’s impact, including who may register, approval, duplicates, roles, and proof.
- Email verification uses single-use, expiring tokens stored in hashed form, with a generic response.
- Internal keys are separate from random public identifiers.
- Profiles, if separate, reference users through a unique foreign key.
- Relationships use a join table with uniqueness on the pair, and symmetry, consent, and deletion rules are written down.
- Every read and write checks the requested record against the authenticated account.
- Database credentials are outside source control and application roles are least-privilege.
“
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
