SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c28ff3184e72a2feaad8e5afce8d54b39903b298e4c9def7b6d71dc313ec9752' 
  AND token = 'R31MZPl0dBCSpDq+q3KJSGn8j/odlHwZMXROlwFzJTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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