SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bf13efe194d81fc4a873323541f01b87e6d791b689dd442fc87f16ee849899ac' 
  AND token = 'K3UeGLvoEiD0K3O+6WFMQzXIWvfzqu7py0u2/4848Dg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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