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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e21f1af90d5fc9e7a3ce722bdec5376ac36a7bab69f52e53ba0cee8ad2482295' 
  AND token = 'UOUuUv3B7yZfjyb0zYz59LVe1a/bYlhoTxlNWhmQi6w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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