SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '02f44d21cc734106aa95de84b451e4a250d7278e9a84280d95ed3731a05cc806' 
  AND token = 'UldoUaWC3Nx7ylQ6tkemHrbCVi/3tRAEzZZkHl+uO0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00073

JSON explain

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