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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6900fbc5048eee1996613e801762cf48651e02def02ec8e0c2b3bba67e316e84' 
  AND token = '2N8xrJ7A65xIzSgzi9m82NvhVLJThI2ZncxdIR8TWGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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