diff --git a/apps/api/internal/service/cdi.go b/apps/api/internal/service/cdi.go
index c8db2ae..4e5f87d 100644
--- a/apps/api/internal/service/cdi.go
+++ b/apps/api/internal/service/cdi.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"sync"
 	"time"
 
 	"financeiro-carvalho/internal/model"
@@ -13,10 +14,58 @@ import (
 
 const bcbCDIURL = "https://api.bcb.gov.br/dados/serie/bcdata.sgs.12/dados?formato=json&dataInicial=%s&dataFinal=%s"
 
+// cdiRateCache guarda as taxas BCB em memória até as 23:59:59 do dia do fetch.
+type cdiRateCache struct {
+	mu        sync.RWMutex
+	rates     map[string]float64 // YYYY-MM-DD → taxa diária
+	minDate   string
+	maxDate   string
+	expiresAt time.Time
+}
+
+func (c *cdiRateCache) valid() bool {
+	return !c.expiresAt.IsZero() && time.Now().Before(c.expiresAt)
+}
+
+func (c *cdiRateCache) covers(startDate, endDate string) bool {
+	return c.valid() && c.minDate != "" && startDate >= c.minDate && endDate <= c.maxDate
+}
+
+func (c *cdiRateCache) get(startDate, endDate string) []bcbEntry {
+	start, _ := time.Parse("2006-01-02", startDate)
+	end, _ := time.Parse("2006-01-02", endDate)
+	var out []bcbEntry
+	for d := start; !d.After(end); d = d.AddDate(0, 0, 1) {
+		key := d.Format("2006-01-02")
+		if r, ok := c.rates[key]; ok {
+			out = append(out, bcbEntry{date: key, value: r})
+		}
+	}
+	return out
+}
+
+func (c *cdiRateCache) put(entries []bcbEntry, startDate, endDate string) {
+	if c.rates == nil {
+		c.rates = make(map[string]float64, len(entries))
+	}
+	for _, e := range entries {
+		c.rates[e.date] = e.value
+	}
+	if c.minDate == "" || startDate < c.minDate {
+		c.minDate = startDate
+	}
+	if c.maxDate == "" || endDate > c.maxDate {
+		c.maxDate = endDate
+	}
+	now := time.Now()
+	c.expiresAt = time.Date(now.Year(), now.Month(), now.Day(), 23, 59, 59, 0, now.Location())
+}
+
 type CDIYieldService struct {
 	accountRepo repository.AccountRepoWithYield
 	txRepo      repository.ManualTransactionRepository
 	client      *http.Client
+	cache       cdiRateCache
 }
 
 func NewCDIYieldService(accountRepo repository.AccountRepoWithYield, txRepo repository.ManualTransactionRepository) *CDIYieldService {
@@ -109,7 +158,21 @@ type bcbEntry struct {
 }
 
 func (s *CDIYieldService) fetchCDIRates(startDate, endDate string) ([]bcbEntry, error) {
-	// BCB API uses DD/MM/YYYY format
+	s.cache.mu.RLock()
+	if s.cache.covers(startDate, endDate) {
+		entries := s.cache.get(startDate, endDate)
+		s.cache.mu.RUnlock()
+		return entries, nil
+	}
+	s.cache.mu.RUnlock()
+
+	s.cache.mu.Lock()
+	defer s.cache.mu.Unlock()
+	// double-check after acquiring write lock
+	if s.cache.covers(startDate, endDate) {
+		return s.cache.get(startDate, endDate), nil
+	}
+
 	start, _ := time.Parse("2006-01-02", startDate)
 	end, _ := time.Parse("2006-01-02", endDate)
 	url := fmt.Sprintf(bcbCDIURL, start.Format("02/01/2006"), end.Format("02/01/2006"))
@@ -128,16 +191,17 @@ func (s *CDIYieldService) fetchCDIRates(startDate, endDate string) ([]bcbEntry,
 		return nil, err
 	}
 
-	var out []bcbEntry
+	var entries []bcbEntry
 	for _, r := range raw {
-		// BCB date format: DD/MM/YYYY → convert to YYYY-MM-DD
 		t, err := time.Parse("02/01/2006", r.Data)
 		if err != nil {
 			continue
 		}
 		var v float64
 		fmt.Sscanf(r.Valor, "%f", &v)
-		out = append(out, bcbEntry{date: t.Format("2006-01-02"), value: v})
+		entries = append(entries, bcbEntry{date: t.Format("2006-01-02"), value: v})
 	}
-	return out, nil
+
+	s.cache.put(entries, startDate, endDate)
+	return entries, nil
 }