SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50272e85895ef269dc008416a4118d58a898b847fa633bf436744873dff1f3d' 
  AND token = 'EUAlx0AoE5lTYnGgojr7yVwBOZ9Sm/jRsBvsICe3Slc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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