SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c81e84a31d744aeedb1c28a20735811c868fbd0c1f06135c4a6ea1c073c861b0' 
  AND token = 'x0npcB3479YbtdssBpSZOEByj4n8fQLCRSz9HZZpzjc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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