SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f8e75962d8eec1fe284a568da768062a168124f6b19e520d154e5c884ef59239' 
  AND token = '3FfNAKUpxjY5sw1pZvg3LR4qYB4ETt6jgwCkAOUkyLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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