SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8239a45fafbb7a4083c9d60e97d5cf3361b155047c2d43b1e47a50efbb86da57' 
  AND token = 'zwUVP35V3BEwM6RpzMSlZg+7Z5AFLtMCAJ+iHslyx0c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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