SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cee1413791e4d1d03f61f0c2f4dec0c4df8b2bb08a331354ea696db495830e0' 
  AND token = 'PExnQzmCn4WnowED+djg/VZw3RhM6spplhKFynxaFBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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