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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '15d6aa7ca9cebb8f6d917eff1e9355d520121ce3aab4d4f500ac536a59a0a85b' 
  AND token = 'SfFk9LCGzSZUawOG3R2A0Si0NROcLYVuz6hmEjsojLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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