SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '476aaf8549929b958d0136cf3c1802e1b15262bb74c043ba270c0cd6feb3d0b0' 
  AND token = 'swZuieBo+UnvZlpwfhxjO7NnFPC2EmxIY8k/CKDcqiY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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