SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6779ca234d4fbd830f63d140ad5ebb023528a62e838cf123014f9c93a623f61d' 
  AND token = '9xmxk/dHjUDveskpBUThlkYHJyQyDi2G3CvjQCnxcwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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