SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21842fb55862c540ab6991caf108f27b3ae3970b90a1fe144c21dc62f8e0a2f8' 
  AND token = 'Qy5pTfW9VnWkY+NBU3ELDuXFHTNjvmGlXPoCqZ0S26s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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