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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20e1c17ff5d73113536175b866923d426713243ef928e670e063d59a15008093' 
  AND token = 'kIp8wYJsRfbgg997PKN7egkY6d4fgzz6A+nWzblVFDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00008

JSON explain

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