SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5324292ca162ff619eeb3d9c9e963bc8c35a69e574247a6b71945873c95f4888' 
  AND token = '5Pm5LlU5ZC2fiYuFJ6DZWDLhVzCOi/wFD1owTqoysB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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