SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '21a1dc9b5c58f1cbc95f4b46004d6f89962dde295f313235a1c1402eaca41379' 
  AND token = 'WlgxtZnHweQrWhsL8+q409/uGlwujPSRYZM3lOKuxt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}