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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4c751f9e4b63cb224cdf9e1c8fb5d30cc948aade2588cc8676af35f6a60e3b3' 
  AND token = 'BqB/khADEc6ZtLy1ESsiJ6qdeGcFLNpm2g3SN1v4Wlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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