SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cd8a8d40ebc80b6b5ace61301d4c75af999bb2dc2f34a2b3c0891eaf7eba551' 
  AND token = 'pZJoKKqq+sCI+9ZNZzwlMBmlDGzRMBOP+5zdA6F7ax8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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