SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b98278caadf85cd3a3afb7309e60878c1a9f7c2fa540ddfb41e1a43648b6926d' 
  AND token = 'vWPiSo6LRR7WcbDPTVxsdsya6dQmUnUAgDlXG/59Mjo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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