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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b9781598ccac8d98f00ca05d535fbb23a888068bb7c2c241fb96eb9576d9d543' 
  AND token = 'Q0srwcvCyj6LiFYlWgUhC53L6Xm+ZtWCmIxevDZ8E8U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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