SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '66ffee2c42421812c17c137b5e007f99d654fc4fa24e77ff5dc6568f35131367' 
  AND token = 'umBX3IoGzLuyPf5bILFmAns7bN8NeeQLPZF5aRb15E4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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