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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c6282c2eeab04a27ccfe1d92730423cfe0831dd68919b8608ba6e1f3cc730e' 
  AND token = 'Kp37di43ayBhu4gRoauZqHqtk6n3XVTrTmpE9qtO4wQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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