SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b52a0dcfdf8624062cbc0a516abdcc7e6e816579555fe7aabde64985a597159' 
  AND token = 'K8biYjP+7MKZYb9i5jqxDxHjBFX2CARQ9yFYHRPjiSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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