SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f275af4429a9978b1aa20bdce9484425a2412e015fa79084b008aa265e360914' 
  AND token = '37GljEoF4TPnxuMVY/F3cbMKNSk7688SMcYyEM6mjpY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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