SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b34a78d094309f48e14d7342245b73f0d19ce1613b867810f26d84cd6b45c2a0' 
  AND token = 'W5lyjZFqxRwL07f0EbIGoJ1KQyq73zJzAbq4ecm73Ys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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