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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc9e725d2f0d7ac1034c5a8123a5a651341fe456a327d9af03c916aae4a41c59' 
  AND token = 'lL7+lDRq+++UfUb0rpiCzhSlvPnryRpk+JXaFJY3kZU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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