SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9df0dd1c29263d86321862fbbc0c16d4de643cc7709d5e23beefa766a39bc336' 
  AND token = 'NNCevIqRRfde1OJIv5v1feRpXqfQrCfhVyk+EaMYoMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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