SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c52598ccf4293370f1a18182e78fd8005c957d4430d31cffe43fa7a91d1814f4' 
  AND token = 'FPbV3DWq27vvXsevF5Ros77FTRosVkaFQBRUlArbLeI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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