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Backend, Data & Security

Learn how the parts behind a screen store data, follow rules, and keep people safe.

01 / Atlas

All Backend, Data & Security terms

Open a term for a simple meaning, an example, when to use it, how official it is, and its code name.

  1. 01 · Core

    Access Token

    An access token is a credential an app sends to a protected service to show what it may do. Rules usually limit who issued it, which service accepts it, its permissions, and its lifetime.

  2. 02 · More detail

    ACID

    ACID stands for atomicity, consistency, isolation, and durability. These four ideas help explain transaction safety, but exact promises depend on the database and isolation level.

  3. 03 · Core

    API & Endpoint

    An API is a set of rules for software to talk to software. An endpoint is one address and one operation in that API.

  4. 04 · More detail

    API Versioning

    API versioning is a plan for naming, changing, supporting, and retiring API contracts without breaking clients. There is no one URL or header style that every API must use.

  5. 05 · More detail

    At-Least-Once Delivery

    At-least-once delivery tries to keep a message from being lost, but the same message may arrive more than once. The consumer must handle repeats safely.

  6. 06 · Core

    Authenticated Encryption (AEAD)

    Authenticated encryption (AEAD) turns readable data into secret data that can be changed back with an approved key. It also detects if the encrypted data or linked details were changed.

  7. 07 · Core

    Authentication

    Authentication checks who a person or service is. It's often shortened to AuthN.

  8. 08 · Core

    Authorization

    Authorization decides what an identified person or service may read, change, or run. It's often shortened to AuthZ.

  9. 09 · Core

    Backend

    A backend is the server-side part behind an interface. It applies business rules, works with data, and connects other systems.

  10. 10 · Core

    Backend Framework

    A Backend Framework provides server tools and shared rules. It can route requests, check data, use storage, and send replies.

  11. 11 · Core

    Background Job

    A background job is a task the server runs separately from the page or API reply that may start it. The reply can finish before the job does.

  12. 12 · Core

    Browser Storage

    Browser Storage keeps data on a person's device through browser APIs. Each option has different size, lifetime, shape, and safety limits.

  13. 13 · More detail

    Bulkhead Pattern

    The bulkhead pattern splits shared resources into separate pools. Trouble in one pool cannot consume every slot needed by the others.

  14. 14 · Core

    Cache

    A cache is a fast, temporary copy of data or a saved result. It cuts wait time and repeated work.

  15. 15 · More detail

    Circuit Breaker

    A circuit breaker stops calls to a remote service that is likely to fail. Later, a few test calls check whether it recovered.

  16. 16 · Core

    Content Delivery Network

    A Content Delivery Network, or CDN, is a group of systems in many places. It serves cached content or edge-made replies from a location near the user. Clear rules control freshness and removal.

  17. 17 · More detail

    Content Negotiation

    Content negotiation is how HTTP picks one version of a resource from the client's preferences and the server's available formats.

  18. 18 · More detail

    Content Security Policy

    Content Security Policy, or CSP, is an HTTP rule for browser content. It limits which files may load and which scripts may run.

  19. 19 · More detail

    Cross-Origin Resource Sharing

    CORS is a browser HTTP safety rule. A server lists which other origins may read its replies. It can limit methods, headers, and credentials.

  20. 20 · More detail

    Cross-Site Request Forgery

    Cross-Site Request Forgery, or CSRF, tricks a signed-in browser into sending an action the person did not choose. The target site trusts cookies or other credentials the browser adds automatically.

  21. 21 · More detail

    Cross-Site Scripting

    Cross-Site Scripting, or XSS, happens when attacker-controlled data runs as browser code on a trusted site.

  22. 22 · Core

    CRUD

    CRUD is short for create, read, update, and delete. These are four common ways to work with saved data, but CRUD is not an API protocol.

  23. 23 · Core

    Cryptographic Hashing

    Cryptographic hashing turns any amount of data into a fixed-length fingerprint in one direction. A secure hash makes it impractical to recover the input or find two inputs with the same fingerprint.

  24. 24 · More detail

    Cursor Pagination

    Cursor pagination continues after a hidden marker in a fixed sort order. It does not count and skip every earlier record.

  25. 25 · Core

    Database & Schema

    A database keeps organized data over time. Its schema says which entities, fields, types, and relationships are allowed.

  26. 26 · Core

    Database Index

    A database index is an extra data structure that speeds up chosen searches, sorts, or rules. It uses storage and adds work when data changes.

  27. 27 · More detail

    Database Migration

    A database migration is a versioned change. It moves stored data and its schema from one known state to another.

  28. 28 · More detail

    Database Normalization

    Database normalization splits related facts into well-shaped tables. This reduces repeated data and mistakes when one fact changes.

  29. 29 · Core

    Database Transaction

    A database transaction is a group of database steps that finish together or are all undone together. Its isolation rules say how it interacts with work happening at the same time.

  30. 30 · More detail

    Dead-Letter Queue

    A dead-letter queue keeps messages that a source queue could not process after its allowed attempts. People can inspect the failure before a controlled retry.

  31. 31 · Core

    Domain Name

    A Domain Name is a readable internet name, such as example.com. DNS points it to websites, email, and services.

  32. 32 · Core

    Domain Name System

    DNS is the internet's naming system. Records like A, AAAA, CNAME, MX, and TXT answer questions about names.

  33. 33 · More detail

    Encryption & Hashing — Learning Bundle

    This learning bundle compares two different cryptographic ideas. Encryption can be reversed with a key to keep data private. Secure hashing goes one way and can check integrity or verify passwords. The bundle is not one standard primitive.

  34. 34 · Core

    Environment Variable

    An Environment Variable is a named setting outside application code. It lets each environment use different values.

  35. 35 · More detail

    Error Budget

    An error budget is the allowed amount of bad service during an SLO window. It equals the part below 100%.

  36. 36 · More detail

    Event-Driven Architecture

    In event-driven architecture, one component publishes a fact after something changes. Other components react later under clear rules for delivery and future format changes.

  37. 37 · More detail

    Eventual Consistency

    Eventual consistency allows copies of data to disagree for a while after a change. If new changes stop and updates keep working, the copies should match.

  38. 38 · More detail

    Feature Flag

    A Feature Flag is a switch checked while software runs. It changes a feature without a new code deploy.

  39. 39 · Core

    Foreign Key

    A foreign key is a database rule. It makes one column point to a valid key in the same or another table. `null` follows the rule chosen for that column.

  40. 40 · More detail

    Graceful Degradation

    Graceful degradation keeps the core job working when an optional dependency fails. The result may be smaller, older, or less detailed.

  41. 41 · More detail

    Health Probes

    Health probes are small checks that tell a platform whether a service is starting, ready for traffic, or still alive.

  42. 42 · Core

    HTTP Cookie

    An HTTP cookie is a small name-and-value item set by a server or script. The browser sends it back only when rules for site, path, lifetime, and security allow it.

  43. 43 · Core

    HTTP Method

    An HTTP method is a word on a request that says what kind of action is intended. Each method has standard rules for safety, retries, and caching.

  44. 44 · Core

    HTTP Request & Response

    An HTTP request is what a client sends to a server. It has a method, address, headers, and sometimes a body. The response returns a status, headers, and data.

  45. 45 · Core

    HTTP Status Code

    An HTTP status code is a three-digit number in a response. It tells the standard result of the request and which result group it belongs to.

  46. 46 · More detail

    Idempotency

    Idempotency means doing the same intended operation again has the same server effect as doing it once. The replies do not have to be identical.

  47. 47 · Core

    Input Validation

    Input validation checks data as it crosses a trust boundary. It enforces the expected type, shape, range, size, and meaning.

  48. 48 · Core

    JSON

    JSON is a text format for sharing data. It can contain objects, arrays, text, numbers, `true` or `false`, and `null`.

  49. 49 · More detail

    JSON Web Token

    A JSON Web Token, or JWT, is a compact format for sending claims between parties with JWS or JWE protection. JWT is only a format, not a permission system.

  50. 50 · Core

    Load Balancer

    A load balancer spreads traffic across service endpoints that are ready to work. It uses rules for server health, capacity, routes, and uptime.

  51. 51 · More detail

    Load Shedding

    Load shedding rejects some work as a system nears capacity. This protects useful work from extreme delay or a full crash.

  52. 52 · Core

    Message Queue

    A message queue holds work or messages until a consumer can handle them. Producers and consumers can run at different times and speeds.

  53. 53 · More detail

    Network Port

    A Network Port is a number that sends traffic to one service on a computer. TCP and UDP use ports.

  54. 54 · More detail

    OAuth 2.0

    OAuth 2.0 is an authorization framework. It lets an app get limited permission to use protected data for a person or for the app itself.

  55. 55 · Core

    Offset Pagination

    Offset pagination skips a chosen number of sorted records and returns the next page up to a set size.

  56. 56 · Core

    OpenAPI Specification

    The OpenAPI Specification is a language-neutral way to describe an HTTP API. It lists actions, inputs, data shapes, security methods, replies, and reusable schemas.

  57. 57 · More detail

    OpenID Connect

    OpenID Connect is an identity layer built on OAuth 2.0. It lets an app confirm that a person signed in and receive standard facts about that sign-in.

  58. 58 · More detail

    Optimistic Concurrency Control

    Optimistic concurrency control lets people work at the same time without locking first. Before saving, it checks the version and rejects a change based on old data.

  59. 59 · More detail

    Rate Limiting

    Rate limiting controls allowed requests or costly actions for one identity, key, or time window.

  60. 60 · Core

    Redirect

    A Redirect sends a client from one address to another. Its status says whether the move is temporary or permanent.

  61. 61 · More detail

    Request Deadline

    A request deadline is the time after which a client stops waiting. Each downstream call should receive only the time that remains.

  62. 62 · Core

    REST API

    A REST API is an HTTP interface built around resources, such as orders or users. Each request stands on its own, uses standard HTTP meanings, can support caching, and may pass through layers.

  64. 64 · More detail

    Saga Pattern

    A saga links several saved steps into one business job. If a later step fails, it retries or adds another step to fix what happened earlier.

  65. 65 · Core

    Same-Origin Policy

    The Same-Origin Policy is a browser safety rule. It limits how a page or script from one origin can read or work with data from another origin.

  66. 66 · Core

    Scheduled Job

    A scheduled job starts backend work at a chosen time or repeating interval. Its rules must say what happens after a late, missed, or overlapping start.

  67. 67 · More detail

    Secure Cookie Attributes

    Secure cookie attributes control how a cookie travels and whether scripts can read it. They also control cross-site use, which host and path receive it, and how long it lasts.

  68. 68 · More detail

    Server-Side Request Forgery

    Server-Side Request Forgery, or SSRF, happens when attacker-controlled input makes a server send a request. The request reaches a place it should not reach.

  69. 69 · More detail

    Serverless Computing

    Serverless Computing is hosted code execution. The provider starts and scales servers, while the team deploys functions or services.

  70. 70 · More detail

    Service-Level Objective (SLO)

    A service-level objective is a reliability target for a user-facing signal during a stated time window. It is not a legal promise.

  71. 71 · More detail

    Session, Cookie & Token — Learning Bundle

    This learning bundle separates three related tools. A session keeps continuity that the server knows. A cookie is browser-managed state sent by set rules. A token carries claims or authority. The bundle is not one standard identity term.

  72. 72 · More detail

    Transactional Outbox

    A transactional outbox saves a data change and a message record in one local database transaction. A relay sends the saved message after the transaction commits.

  73. 73 · Core

    Transport Layer Security

    Transport Layer Security, or TLS, protects data on an untrusted network. It hides the data, detects changes, and checks who is at the other end.

  74. 74 · Core

    Uniform Resource Locator

    A URL is a network address. Its scheme, host, path, query, and fragment tell clients what to open.

  75. 75 · Core

    Web Session

    A web session keeps related actions connected across separate web requests for a limited time. It often links a hard-to-guess ID to state stored on the server.

  76. 76 · More detail

    WebAuthn Passkey

    A WebAuthn passkey is a public-key sign-in credential that resists fake login sites. Depending on the provider and authenticator, it may sync across devices or stay on one device.

  77. 77 · More detail

    Webhook

    A webhook is an HTTP callback sent out when an event happens. It tells another system to react.

  78. 78 · More detail

    WebSocket

    A WebSocket keeps a two-way connection between a web app and a server. Either side can send messages while it is open.

  79. 79 · More detail

    Worker Concurrency

    Worker concurrency is the number of jobs that consumers may run at the same time. A limit protects the server and the services those jobs call.