SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ef2f572cf8f14c6fa19c403542806145897e7ffd70c5be5d1fb65764c868565' 
  AND token = '521WDLsDK1I59ale3kYqOnTsTD/ePYPcx80sAjpJH8Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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