SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1553d42444e2041c06a7aadc118dca905d8e7fb294b4db2089f579c4857b8256' 
  AND token = 'cMSnAuYWseLt8QjqAo7tPj10u+TZeJetWeUqo+LnXc0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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