SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81d18c4d0560219669e50738ce544aa16aa8fefc91a019b0d820f40cacb1bc43' 
  AND token = 'OYyiUwR48zGulIUrU0ARgDcPOf5chnvBIrcBI0mOZbg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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