SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c49d356886756352ce03fab3a1f457edc69ce9a47521287f97607214734edf' 
  AND token = 'QMo4iSJaLuY2NlLLTGk0ZsqzwaEy4SwT9DI4amrGZ0U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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