SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40112cbd56dbbf901d779778294178e15500a744b6127b21787ec349a9912cc3' 
  AND token = 'nInDwo5ZkyJrElRImHis35G4n4oFiBkju2BYsIjaI1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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