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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '156a664340396e36d4f99a71a9a0201477a40b6530384ac059e84eda4091380d' 
  AND token = '99ZI4Vux2Xv4rZJtEjIZ42+cxmAVesYI7uTnAgZDO4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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