SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9ce287768adacd52dcbb2ac68d6f51aafc6baf3a3f4cf02567a7e41797d66ef' 
  AND token = 'lH5BjQMUNBIDy6mc3RpaWp/Mzv2hNmlw4SLLq9Gt+Vw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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