SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f81488fa203e76ba60af4498390364dd75ce9a7218123c12d38f6b3ca5e17f60' 
  AND token = 'vmxpFswl8wyYB0tZRkZfSDxpLU7jDKUD12677G/Tp4o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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