SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6d7a9d6d3651ead8e73447a98b6f01a6bad078d6da5bcd0231e27e550d52791' 
  AND token = 'XNsVzqmi2gFvRMe6I29mhzHVZM4hmbAXP9sZQKc+hj4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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