SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff5f804653dda4db9fc83a3121baac42d7949b417e8d5dc52d223479e55c3d76' 
  AND token = 'RnlhZvMZY6UFqy93kL3uRcUgwm+lXzI/g3XaPCs2FgM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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