SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54b810549805b6d90183af319395c52ad8441ed7a18209e45059fb041397f39d' 
  AND token = 'yESIX5EZh27btJ+iUhEW3hxu3pu7apfOlZBWbFaDMrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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