SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd0f0b7f92256b5be41f19fd94234724262575bfc052cb8389b262f5a3913e9a1' 
  AND token = 'xD3fp9KOIgW7d6mrRQ/qFCDYTQfxwiOsPQCSYdogQEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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