SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8692b2da71b666274580e0d55f61311c6da3678c4780dc354d97ec34433ad722' 
  AND token = 'T4b7dQGEOkmgz4qpMvBzTyIb+5UJBd3yo4vdVG2AjDU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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