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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b97d6dd520134ba01e1ceed8fd34836effc9275d9ca8bae7461cf40d4e0c1356' 
  AND token = '8l97QDLwRpyjpW2lcuE7FrkfcAqS6pX4TAlET9+wweM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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