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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6cdf9205993e1c58e23ee0b8f060cc5e55178e8cff8185e71801b76944c972c5' 
  AND token = 'U8W/XVIVJi9oerHm9d4LXtdz3oT2zwPyIdVT1XAuCIw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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