SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d656615a3a85bad44cb57296ea00d231fff7e6e99898bc1a89603f5efa99f21' 
  AND token = 'eg3V8HxAnmsC0DG2eELDIsbdznKjB6aHsibBB1pDmWo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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