SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12d2945ccf5c578d353593ed8a269dcd5646b6fd9bd408c1de001a5945c3808' 
  AND token = '0hJm7BSuqI+BnzKi/TzSsX0R6bDQzBz3zD8jPFJKkJ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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