SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b994df70a7ad89140eaa796508a45ab729e28c85b572c7931c422c237aca168' 
  AND token = 'qtwEvAW6rBPm5jLkJ1x5Hi5jUvRPJViMUPzVYduEjVA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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