SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '608c9c9313513c994f0b388747c4e2714e4f8047046dccddc717f37e3c575129' 
  AND token = 'Y/oGPaYDwUJBIzFC78brRp57g4cUNdJsCK60vmV+75A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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