SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdbecc978188b575da975325d96044e9b573248904965c2fc088995a0584efe9' 
  AND token = 'UOmbUZcDrC+8BkU42KwwW1ec3ZSFlFXfeyVlgGP9d8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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