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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3c615997ed803e21fb17f9e4976e3d674bd4285aa2e5d3bfb3f976074c6d1e13' 
  AND token = '0s/1N6SLWcaoxFNBtA65bTOHH77QaK+pAor1dlT2dKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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