SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '43d31d44ed48cedef22c1d224f021d50085eee9d5496dac4ad107e90c5f4a884' 
  AND token = '/Lv+3JMB6Km1rSLTHuDZyKMFHRfXftsKGZJvywQvX/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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