SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e78873d5e2f9a5757e2cf65420d158ee9a978551e87cece1f5c2166e15a7abc' 
  AND token = '5kJGG861rywBL9RJM5de4wHcueTUls3wrYDLoIoMQLw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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