SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b1cdac3b8fc38950f34cd302c895783daaf044658b8668162b40f9d257ea74' 
  AND token = 'uPOrSNpCJTIN2DoXsFRm0DsAEeFeLyf//GetdFHCSew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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