SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '048971c29f70c9fe4e1060b55e0a72bfbea5c8f3a139986019a9468a55d05e5e' 
  AND token = 'mBZXi7i/r2CYzZ/KWN1pUfbSfmGgI6MeJfNIMSGLqQQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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