Expiring key-value store

Your task

Build an in-memory key-value store with set, get and delete.
A write stores or replaces the value for a key.
A get returns its value or an explicit missing result.
A delete returns whether a key was present and removes it when present.
Empty strings are valid values.
Keep separate stores independent.

Required API

NewExpiringStore
func NewExpiringStore() *ExpiringStore
ExpiringStore.Set
func (s *ExpiringStore) Set(key, value string, ttl, now int64)
ExpiringStore.Get
func (s *ExpiringStore) Get(key string, now int64) (string, bool)
ExpiringStore.Delete
func (s *ExpiringStore) Delete(key string, now int64) bool

Constraints

For this part, every operation occurs before the stored value expires.
Keep the provided ttl and now arguments in your interface; expiry behavior will be introduced in the next part.
Keys are valid case-sensitive ASCII identifiers, 1–32 characters.
Values are ASCII strings, 0–64 characters.
At most 1,000 operations occur per store.
Use only the standard library.

Examples

The runner calls your functions directly; you do not need to parse JSON.

Example 1 · missing

Calls in order; values are shown as data.
Call	Returns
`NewExpiringStore()`	Instance 1
`instance1.Get("x", 0)`	Missing (found = false)
`instance1.Delete("x", 0)`	false

Test data

Input

{"ops":[["get","x",0],["delete","x",0]]}

Expected output

[null,false]

Example 2 · empty and delete

Calls in order; values are shown as data.
Call	Returns
`NewExpiringStore()`	Instance 1
`instance1.Set("x", "", 10, 0)`	No return value
`instance1.Get("x", 0)`	""
`instance1.Delete("x", 1)`	true
`instance1.Get("x", 1)`	Missing (found = false)
`instance1.Delete("x", 1)`	false

Test data

Input

{"ops":[["set","x","",10,0],["get","x",0],["delete","x",1],["get","x",1],["delete","x",1]]}

Expected output

[null,"",true,null,false]

Related guides

Review Code Boundaries by Finding a Cache Expiry Counterexample

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