SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3d3984bb21703f431d438a93f79d6748232309005faabdaa1024b045425f008' 
  AND token = 'PUrTpJZhTTqCzdjpgZiroFhu0XNZh7H8+HDEKboxC08=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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