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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '547f9e366e04add0db6919ad75f401742252145154535be8bfdacde0868ec9ff' 
  AND token = 'K08qmvCtpEj4mpMqh58NshynnakC5CkKEo2ePiJBQkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}