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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1c592af1bff1a3ab0deffad539c60bd31357ea242a84adc5862b822d33bccba2' 
  AND token = '39JLhH0U8BOHR1w3iOIxWqqlQpXj5r10GJD3QgaTW7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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