SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b92808ed551a7aeee84bba1f0c8fa45ce4630a83b34762d219ed100ea893431e' 
  AND token = '16j2td+JojTxOz7f6NIXmXTwJjzvKqcTYrwX4DbGmwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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