SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '39eb43cef5277a588d2dcb56951210b8cd73ea3261e82494152f06a408d6ee75' 
  AND token = 'KGt5B/BtLnIWMurJESLLr4jlBqfCnUQZUINN1pR30Kc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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