SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '208f5187731ce50e147937a478a54ac9314e1b6a7ffb6017f93a9cc162392262' 
  AND token = 'SydLShdyzp6NEE1P3Ebd/DzYxnGbGGliQBDhmCGziiI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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