SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '510a15b842fc37e0326140f18384c8d6635511eed199da23e658f9eaf0f0aef8' 
  AND token = '85ZK1GGUKJ3M7eERDDY91mejn0HhYjAioLgWe4hzXdw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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