SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ab9a4c1415fa79d0336cfb12055d237798551aaa30d73399f47afa53b006f81' 
  AND token = 'hM6xxfyJ4HVaNuBMjHwX07j/SaycwVyWuUhXEdQ7wvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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