SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f31156d4696856fc5db1a5d01f2ab2f1df79cf09b4ee1dc25e8ade2421ffa0a4' 
  AND token = 'BMjVafdp2NfbdPVWXdfPxcnqLy+nTTmlqrIgRwwKtNs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00111

JSON explain

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