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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ebf939a3cf8da04baff7785970f946ccfbbbb07159c9830f334627da9c9bf761' 
  AND token = 'kpayLzmKStGacME5KXXTY6d8nHflT7wwHkesOxAB/xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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