SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ad25fb065438b19a87651800a781e1ee04eefa7086a403a6927d65dca95c531' 
  AND token = 'qKkhKacN3dKt/vm6reIEm5w5xcuqAFlTbbDkJejvLpI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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